CC is doing a "Buy Endwar for $60, get Rainbow 6 Vegas 2 for free" deal this week, B&M and online.
R6V2 is a pretty good game, a $40 value, I believe. Trading it into Gamestop will probably net you $10 or so, so you'd essentially be paying 50 for Endwar if you do that. Or you could just keep the two games.
Too bad you're not looking for the PS3 version of Endwar, Amazon matches CC's deal and reduces it to $40!