Pokemon Emerald - 3rd gen mechanics are the best. Honestly, I think this was a very formative game for me, mostly because when everyone else was doing whatever kids do in middle school and early high school (no, actually make that all of high school lol. and college), I was EV training new Pokemon to find new and creative ways to win in the battle frontier. I actually only recently got back into being serious about Pokemon, because the 4th/5th gens seemed like such a letdown after gen 3.
Metroid Prime - I'm really stunned at how well this game still holds up. It just feels so good to play, to look at, to hear. I vividly remember my first time through, really sweating out multiple segments of the game (Thardus, Omega Pirate, Phendrana Drifts research labs). Metroid Prime is probably my favorite boss of all time. How did Metroid Prime 2&3 drop the ball so hard?
Fire Emblem - Path of Radiance - Great replayability, since there are so many different characters. All the minor characters are so interesting. All the plot threads, minor and major, are exciting. Ike is really a guy I can get behind and cheer for (I guess it's a bit strange for me to be cheering at my TV during a text-scene, huh). I get so excited by these things that the fact that the game is a lot of fun to play is almost an afterthought to me. But make no mistake, it's fun to play. My only complaint is that a character can only have 5 supports. I want to hear all the support conversations!!
Yeah, so Fire Emblem Awakening has that (you can hear all the supports you ever wanted), which is great. All the characters are a lot of fun, too. But Chrom is no Ike, I could never really get pumped up for Chrom as I did Ike.
Legend of Zelda - Wind Waker - That part after you get your butt kicked by Ganondorf, and you basically get told 'welp, better explore the entire world to see if you can find stuff to power you up'. Yeah. Hopping from island to deserted island on my sailboat, man do I feel like an intrepid explorer. I wish I could erase my memory of this game so I could experience it again for the first time. Now I already pretty much know where everything is already. I never quite got that feeling from any other Zelda game (or any other game, for that matter). I think it was the boat. Too bad Phantom Hourglass blows.