Gundam 3D Battle - It's an enchanted port of Gundam Battle Universe, one of the best PSP Gundam games. This version includes suits from Gundam Unicorn episodes 1 - 3.
The Level 5 Games - You can't go wrong with Inazuma Eleven Go, Danball Senki and Fantasy Life.
Inazuma Eleven is an RTS with a soccer/futból skin with a simple plot and charming characters. The Go series is completely 3D and contains more depth than the standard trilogy.
Danball Senki is a more advanced Custom Robo. The latest game, Danball Senki Wars, combines the Custom Robo combat with an RTS system that's somewhat similar to Inazuma. The prequels, Baku Boost and W, are similar to standard RPGs in regards to exploration. This is my fav Level-5 series since each game gives you a large party and a ton of customization options.
Fantasy Life is Final Fantasy mixed with Animal Crossing complete with online multiplayer, combat, and a soundtrack by the legendary Mr.Uematsu!
One Piece Unlimited World Red - If you like One Piece, then you should get this game. It's a boss hunt like Monster Hunter, but you get to utilize the Straw Hats' Post Time Skip Abilities and explore a rather large hub world. The combat is WAY better than Romance Dawn's. Also check out the prequel, One Piece Unlimited Cruise SP. It's a massive game that includes the two Wii Unilimited Cruise games and some extra content based off the Marineford Arc.
Initial D - It's free and has online play. Try it!
http://img28.imageshack.us/img28/4846/w117.jpg Official Pope of the Church of Headless Tiida