Mark's #3: Memoir '44
I'll keep this short & simple... it takes the brilliant "Command & Colors" game engine first seen in Battle Cry and knocks all the rough edges off the design. Memoir '44 covers (at this point) much of the European theater of WW2 with a wide variety of 'official' scenarios and 2 boxes worth of expansion stuff (with two more promised expansions in 2006!). The game is supported online with panache & flair by Days of Wonder.
What's not to like? It's my favorite "wargame", hands down. Now, I fully realize as I type this that "real" wargamers are wailing & gnashing their teeth when I call Memoir '44 a "wargame." But as I've said before, I'm a reformed wargamer myself - and I've had more fun playing Memoir than I ever did playing Squad Leader.