All these are good suggestions.
If you are only looking for exclusives get ED (15 bucks at gamestop if you can find it), RE 1 and 0, Pikmin (20 bucks). Metroid Prime will sell for 20 bucks starting the end of April, this is one of the best games for any system this generation, period. F-zero will sell for 20 bucks at the end of April too.
I also heavily reccomend Beyond Good and Evil (20 bucks), a steal at its price. Pick up Freedom Fighters (20 bucks), Metal Arms (20 bucks).
Most of the 20 dollar titles can be had at Best Buy for 15 using the Gamer's gift card.