Pokemon. Oh yes, ever since I picked it up 14 years ago. Not only have I done thousands of online battles to great success, achieving the top 200 out of thousands of players, I have completed Gen 1's dex twice and gotten 12 Gen 1 Pokemon to lvl 100, I have completed both Pokemon Stadiums to the end, I have completed Gen 2's dex and gotten 6 Pokemon to lvl 100, I have a Gold Trainer Card on Gen 3 and 6 Pokemon at lvl 100, and finally I have a Black Trainer Card and 10 Pokemon to lvl 100 on Gen 4, and I have beaten set 8 of the Master's Battle on Pokemon Battle Revolution. My Pearl version alone has over 440 hours on it. Generation 5 is currently in the process of conquering, and I was going to get cracking on it sooner but I've decided to do it on B2/W2 so I'm holding off until then. To this day Pokemon is the only game I do serious competitive multiplayer with. Really, I normally could care less about multiplayer besides the casual having fun sense, except when it comes to Pokemon.
Also, possibly, Tales Games, Star Fox 64, any 3D Mario Platformer, Muramasa The Demon Blade, and some of the Sonic games. Pokemon essentially made me good, or at least attempt to be good, for any JRPG I've played.