I've had an xbox 360 for a long long time, well a few of them actually. However I have never used it enough to really dip into the xbox arcade. My only experience was the first year or two of the xbox 360's life when the live arcade was a bit lacking. Years past and I don't know whats what. Surely I could sift through threads and articles on the internet, but I want people who play games consistently (well, why else would you be here), I want your opinions. The only must-haves I can think of is Doom, Doom II, and of course Duke Nukem.
Preferably staying away from multiplayer games, I would rather have the game and my console out live the need of a player base to enjoy it.