i own/recommend

banjo kazooie
mega man 9
bionic commando
Alien hominoid
Prince of Persia
castle crashers
braid
Super Street Fighter 2 HD Turbo Remix


other games i own

geometry wars
street fighter 2 HF
Super Contra
Hexic
Undertow

Castle crashers is great.
SF2 hd remix bla bla is incredibly pretty but gameplay wise... well it's a very old game, it's not great. Still the artwork is beautiful.
Castlevania is great.
Puzzle quest is great.
Penny arcade games are both fantastic.
N+ is very good if you like platforming. Can be crazily hard though. I got an achievement for dying 1000times and have probably gone on to earn another 500 or so.

Whatever you do, do not buy Bionic commando rearmed. One the worst games i've ever played, awful, awful, awful. The gameplay is as clunky as can be. It is simply frustrating.

This is borderline horrible single player.  HOWEVER, when you get two or more involved, it takes on R-Type proportions of being a real good shooter.

People should take a look at community games also.  If you want an Amiga style side scrolling shooter, Weapon of Choice is worth looking into.  We are talking old school, start over from the beginning style play, it provides some innovations worth looking into.

Live Community games is a source for games ignored by a lot of people.  This is where something new and innovative is likely to pop up.

It really depends on what your looking for - There are at least 2 dozen 'great' XBLA games, and tons more that are good if they're your cup of tea.

I'm not the most experienced with XBLA, but most of the recommendations so far have been along the lines of the 'must have' games.

I can't want to start development on my XBLA/CG game :)

i recomend "pacman" its an age old classic.................or "zuma" both are good, id have a look through coin up classics and get "double dragon" its mint

frogger?