I downloaded out of the park baseball 10 the other day -- It's absurdly complex... It's a text-based management sim, for those not in the know. Analytical Sports Nerds only need apply, as this thing goes above and beyond comprehensive. Do you want to start a league in 1976, using only triple and double-a rosters? Fine. Do you want to have a contemporary career with the Korean baseball leagues? Fine. I BS Thee Not, it's that detailed.
For the 'ongoing review Trav writes for lack of other hobbies', while I want to do a Mariners and/or Rangers modern thing eventually... I'm stepping back a bit. This career will begin in 1995 with a 21 year old Trav as an unemployed wannabe manager (Yes, you can do that, too.)
Most likely, I'll only be able to get a job with some rookie or Summer-A league. I tried a test run with modern settings, and ended up as a manager for the Arizona League Indians. It's a frustrating experience, in a good way... You finally get that number four hitter, and then the GM calls him up to summer-A ball, leaving you with five reject pitchers for your trouble. Then you try to find a way to work them into the rotation while they're busily bitching about the outrage of getting sent down to the cellar.
(Edit: I googled the AZL Indians out of curiosity... The rosters were accurate. It's kind of insane to me that a game designer would be so meticulous to update accurate rosters all the way down to the bush leagues. If for no other reason, that attention to detail impresses the hell out of me.)
Thus far, the game is pretty awesome. If you're an uber-nerd, of course.
(Edit #2: Any league from 1871 to 2009 is supported, with historical updates as you progress.)