any system, any genre, any year. mine would have to me ghost trick for the ds! its short but its such a charming story and characters that im always drawn back into, and a really fun kind of puzzle game. if anyones looking for anything to play like..... check it out 👀 professor layton and ace attorney games are also near and dear to my heart. how about you guys?
be my friend
Personally, one of my favorites is Pokemon Mystery Dungeon: Explorers of Time. I loved the story, and all of the characters and how they mingled with each other. And the soundtrack was amazing.
Then when it had a remake, it was so exciting! One of the best parts that they did was add those bonus episodes that focused on characters that weren't the player or their partner.
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It's a three-way tie for me between Super Metroid, Duke Nukem 3D and Fallout 4. (Well that kind of shows my age. Heh.)
Skyrim I believe, I always go back there.
I think my Absolute Favorite Games of All Time are Fire Emblem 7 and The Last of Us, both for their excellent gameplay and amazing characters. I could probably spend a lot of time analyzing The Last of Us's characters and nerding out over its setting (I'm a sucker for urban decay/post-apocalyptic fiction), so if anyone ever wants to cry about this game with me, let me know. :')
Persona 5 and Tales of Berseria are pretty high on my favorites list as well, but they haven't impacted me quite as much as the first two!

Tetris in general, but Tertis Worlds on the GBA.
I think only Pong is older.
How I wish there were a portable or reinvented Tetrisphere.
Skyrim because I can't seem to go to anything else on my PS4 ... I always go back to that game.
Buuuut.... I'll have to say Pokemon, any generation for the handheld systems. Too much nostalgia with those games.
Sims any of them really but sims 3 supernatural pack was my fav. I love the sims!
I feel like there's two answers for me. I immediately thought of Kingdom Hearts because that one holds a special place in my heart. As does The Sims. I can't decide on anything newer because I've played so many great ones e.g. Dragon Age, Mass Effect, The Witcher 3.
Edit: efhewiufhe I forgot about Majesty. That's also a childhood favorite.
Half-Life. I've come to terms with not getting closure for the series, I can still appreciate it for what it is and make up my own ending :P
A close second would be a tie between the Fallout and Metal Gear Solid series (excluding Survive because that's not a Kojima developed game and was awful).
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Assassin's Creed 2.
A close second and third would be Skyrim and The Witcher 3.
(Yeah, I know that I'm all Overwatch all the time and I love that game but the lack of lore updates, character development and singleplayer just tinge that so badly and I'm getting tired of lack of updates.)

Ah that is a tough one for me because there are a lot of games I used to love growing up that I don't play anymore and new games that I love that I still play. My top two are Resident Evil 4 and Fallout 3 GotY edition. A close third would be Assassin's Creed Brotherhood.
I hear you on overwatch. I have been playing a ton of Forza motorsport and Horizon 3, but I wouldn't consider them anywhere near my top 5 list. And I am shocked that Brotherhood is not in your top 3 :O