Just the 3DS Pokemons (XY, ORAS, and S&M), Xenoblade Chronicles 1 for the New 3DS, and the 3DS Fire Emblems (Awakening and Fates).
If you have played the earlier gens, then
Pokemon X & Y is a disappointment. You get a team wide exp share so you don't have to pick one or two main Pokemon to focus on. You aren't lacking for money to buy potions to heal up, and the enemies are not threatening enough. There is no interesting world design. So the game is overall easy and boring. There is also almost zero side content or postgame to do after beating the story. There is just the short Looker storyline that you will finish in a couple hours, the battle tower. The battle tower's extra facilities having been removed, so now it's just simple 1v1 or 2v2 runs and that's it. The transition to 3D was poorly executed and the game is an aesthetic downgrade from the prior games (including the 3D GameCube Pokemon RPGs, Colosseum and XD, by Genius Sonority). The story is also overall boring, and the main antagonist is poorly written, which is shocking coming off of Black & White which had a genuinely very good JRPG story. I also wasn't a fan of how mundane the new setting of Kalos was. It did not feel like a unique fantasy world unto itself like prior gens. It was just real life France.
However, the game is only a 20 hour long commitment, and I thought it was overall solid enough. I didn't like most of the new designs, but you get Mega Evolutions which are cool. A couple of moments got me a little teary eyed (Professor Sycamore's letter, the AZ subplot, and then the Looker postgame quest). You'll want to play XY anyway to transfer your Kalos favorite designs out to ORAS (not sure if the Pokemon Bank is still accessible now that 3DS internet service has been terminated, you might need two 3DS' or need to use some sort of online service).
Pokemon Omega Ruby/Alpha Sapphire is not a replacement for the original RSE on GBA. The original RSE was more challenging, where you did not have team wide exp share, constant teleporting, or easy access to healing. It was much more of an RPG where you had to wisely spend your money, stock up on items for the long journey to the next town and the attrition that involved as you bushwhacked your way through the marsh in the middle of storm, and you had to decide which Pokemon you would focus on levelling. The GBA version also had better aesthetics. It might not look like it if you just google screenshots on your LED monitor and see emulator screenshots, but on the unlit GBA screen the world had a much more desaturated look that made it look like 90s cel anime backgrounds. It looked more like the rough outdoors. ORAS' world on the 3DS however, has a much more oversaturated and brighter look to it and feels more plasticky and fake. The ORAS version also traps you a lot in long, unskippable cutscenes, which wasn't a thing in the GBA version.
However, the upside is that ORAS has far and away the most content and features of any 3DS game (I didn't buy USUM). Once you beat the story, you get easy access to nearly 500 Pokemon, including past legendaries from other games like Reshiram from BW. And you also get more mega evolutions. So you can run around with pretty much almost any of your most favorite Pokemon in the franchise released up until that point (except for Kalos Pokemon, which you will need to transfer in from XY). I consider ORAS to be the last hurrah of the franchise. I somewhat regret transferring all of my Pokemon from ORAS to S&M. I wish I had left them on ORAS.
Pokemon Sun & Moon was the last Pokemon game I bought, and was where I stopped. S&M has major issues with its story, which is the longest to date, and constantly traps you in long unskippable cutscenes every 5 feet. Now, I like story heavy JRPGs, but GameFreak is awful at executing them. S&M is very story heavy, but it isn't even about you the protagonist character you are playing as. Instead, you are standing there as a bystander to the main heroine Lilie, who relies on you to solve her family problems for her. It feels like either the protagonist should have been allowed to talk, or Lilie should have been the character you were playing as. The story also has a copout ending. If GameFreak's writers wasn't going to follow through on the consequences, then they shouldn't have set them up.
The setting is also just Hawaii, and yes it is more appealing than Kalos but it still doesn't feel like an immersive fantasy world like gens 1 through 5. And before anyone says "well gens 1 through 4 are based off of Japan!", I have spent years of my life watching hundreds of animes and live action movies and playing games set in Japan, and those early gen settings did not feel like "oh it's just Japan" like how the later gens feel like copypastes of our world.
The same fundamental gameplay issues in X&Y are here too (no challenge, nonexistent world design, no side content or postgame, etc). Transferring Pokemon from ORAS here was a mistake IMO, because you can't bring your Mega Stones with you, and most Mega Stones in S&M were unobtainable for regular players and could only be gotten from limited time online distributions, so you would need to cheat to get them now. And even if you did transfer your favorites in from ORAS, you have no postgame content to use them for. It's just more 1v1 and 2v2 battle tower runs which I had already gotten bored of years before.
That being said, it's only a 20 hour long campaign and generally pretty 5/10 okay. Some of the characters are pretty funny. I liked a few of the new designs. Some of the music is neat. But the 3DS generation of Pokemon games and the XY anime's bait and switch robbing Ash of his league victory really soured me on the franchise. SwSh was announced and looked unattractive, and then we found out about Dexit. That was the last straw for me. Since then I have only occasionally popped my head in to look at the new anime movies and show.
I preordered
Fire Emblem Fates so I got the version that had all three versions in one + DLC content. I must have sank 200+ hours into that game and touched the third route or finished all of the DLC content. Sadly the English localization was bastardized by Nintendo Treehouse, but there is a fan translation patch. This game has quite a hatedom against it, but I thought it was okay. Honestly, Fire Emblem plots are usually never nothing to write home about. I did felt disappointed by Conquest, though. The premise is that you stick with the evil empire and conquer the Japanese kingdom, but you don't get to do that. Instead, it turns into this bizzare imitation of World of Warcraft where you're on the side of the conquering faction, but you play as characters who are doublethinking themselves as the good guy heroes. I wish I could have just been a straight up evil conqueror. For Birthright, the medieval Japanese aesthetics were quite refreshing.
Xenoblade Chronicles 1: the game is overrated (mainly by people who haven't played many JRPGs), but it is very good nonetheless. It has good cutscene direction and an above average English dub. The first half of the story is engaging as the protagonist sets out on a manhunt for a mass murderer. After reaching Prison Island, the tension deflates and the story becomes boring "kill the angelic god monster" schlock, but it's still worth finishing. I found most of the cast unlikeable, I only liked Shulk, Dunban, Dickson, and Riki. While the setting is conceptually interesting (the world is set on the backs of titans), most of the actual environments were rather boring to walk through and look at. The MMO combat is meh. The sidequests are bad and a waste of time. Some of the musical tracks are memorable.
I might sound like I am being overall a downer (I get accused of that a lot), but I think all of these games are solid and are worth playing. Just go in with tempered expectations.
As for DS games, I am not going to do a comprehensive list. Off of the top of my head, the worthwhile ones are
Final Fantasy Tactics Advance 2, the DS Pokemon games, Pokemon Mystery Dungeon Explorers of Sky, and... I am struggling to think of any others right now.
Final Fantasy Tactics Advance 2 is my personal favorite of the Tactics series (Tactics Ogre, PS1 FFT, Ogre Battle 64, etc). It has the most fun combat and character building and at no point does it feel frustrating. The game is themed after light fluffy adventuring with a huge amount of missions to go through, as opposed to a serious plot of a set duration. There is also no permadeath of characters. The prior Tactics games are frustrating and stressful because you are trying to feel out what you can or can't build with the system but the clock is ticking and you are approaching the end of the game and don't know if you are going to have that cool spearman build you were dreaming of before the end, or if it is even possible. And ofcourse, you are constantly trying to keep your guys from not dying, and then resetting if they do die. FFTA2 just sidesteps all of that, if someone gets KOed for the mission then no biggie. The main story is short but inconsequential and there is a lot of missions to do after that, so you just keep playing and trying out different builds until you are FFTA2ed out.
Pokemon Mystery Dungeon - Explorers of Sky: it's a roguelike. The earlygame is meh because you're not high enough level to learn cool moves and don't have enough money to buy any, and don't have a large party to command yet. Once you reach the midgame and your options open up and you have 4 party members and you're customizing their moves, the game gets pretty fun. That being said, the gameplay begins to wear out its welcome around the 40-50 hour mark, near the end of the story. The story was surprisingly good, probably the best written story in a Pokemon game I've played (not going to oversell it as super amazing, though). There was a postgame storyline which was okay. Has some great tracks towards the end of the game.
Pokemon Black & White: the first story heavy mainline game, but executed well. You're not trapped in 5+ minute long unskippable cutscenes every 10 feet. I overall liked the cast. Probably the best story in the mainline games. The new completely brand new roster of Pokemon was exciting. The Pokemon League was brutal and I game overed on the final boss, and beating him felt really satisfying. I disliked how linear the world was, and the lack of side activities like Pokemon Contests or the Trick House. The game did have some postgame content in the form of hunting down the Sages.
