I've been through a decent number of machines, nearly all being reasonably priced.
Demo Man is probably the best game that can be realistically had for 2k.. good call outs, incredible flow, decent depth and fills the DMD requirement of young nerds.. of course, for me Taxi is the best pin ever built, so that's the best deal in pinball.
JM is a snore pin, crappy call outs, worst video mode of all time and the nap time glove is beyond the last nail in the coffin, it's tapping the dirt down.
A few years ago The Shadow would've been undisputed king of the 2k hill, but that train left the two grand station and hasn't looked back. (still.. in the justifiable range vs Wh2o, which commands stupid money)
BSD deserves mention but i think it's too hard for average joe to be a great pin to anyone but pinballers with a good bit of flipper skill.
FT deserves runner up.. can be found under 2k, approachable and playable for new guys, but very difficult to accomplish super jackpot which keeps the skilled player happy.