[The Z]

It depends what you like. If you can stick with a game that can occasionally be frustrating, but is very John Woo-esque, than Dead to Rights is alright. If you like flight combat (but not very big on simulation) than Crimson Skies is good, if a little short. If you're looking for a good story and don't mind not having to press a lot of buttons and be extremely active, Dreamfall: The Longest Journey and Indigo Prophecy are solid.

Jedi Knight 2 and Jedi Academy should be fairly cheap.

Soul Calibur 2 might be under $20 now if you're looking for a good fighting game.

Prince of Persia games are fun action-adventure games, although only the first one is only $20 I think.

If you're looking for a Diablo-like game (but not nearly on the same level) the Baldur's Gate: Dark Alliance games aren't bad, but I found them way more fun with someone playing with you.

Syberia's a pretty good adventure game that's in the same vein as Monkey Island (you can't get stuck or die, but some of the puzzles are a little confusing).

X-Men Legends is pretty entertaining too.