Dark, you can't play madden online with the Box. You see EA made it's own servers, hence PS2 online Madden, and refuse to use MS's so Box users can only use Sega and MS sports. I figure you have:
Halo
but I recommend
Buffy (I know it sounds gay but great game)
Rallisport (Ralli game, great)
Splinter Cell (Stealth)
Morrowind (RPG maybe not your style)
Dead or Alive 3 .......or ...Mortal Kombat
Max Payne (Action, amazing)
Dead to Rights (Not quite as good as Max)
Unreal ( great FPS)
Sega GT 2002 ( Racing )
Deathrow ( futurisic sport, give it a rent, I love it)
The Thing ( great adventure)
Tony Hawk (Skatter game, rent it, it's great)
Enclave (cheap and a fun, hard adventure game)
Jet Set Radio Future ( Cheap fun game)
Ghost Recon (great Clancy, stratgey game)
Conflict

esert Strom (you get to kill Saddam do you need more)
Genma Onimsusha (If you dont have ps2, games awesome)
my favorite
Hitman 2 .......This game is SO much fun
Anyways, I have a PS2 and Gamcube and the Box is my favorite. Not saying the other 2 are bad but, the PS2 titles I like are only GTA and RPGs. The Gamecube has Zelda and Metriod but I love the Box's live feature and the fresh games coming out for the Box. I don't want to sound like a racist fuck but most of the games for the Box are American and I like the games they produce as opposed to the Japanese.