What's the best entry into the series? I'm kind of looking for something to play and that seems as good a thing as any. I got started with Diablo and was into that for a few days but honestly I got my fill of hack-and-slash button-mashing dungeon crawlers back with Ultima I.
I've been playing a little bit of Doom (maps great to an Xbox controller) and Secret Agent (likewise). Did you ever play Secret Agent, or any of those shareware Apogee games? Crystal Caves, Jill of the Jungle? They used to sell floppies of the first of three "episodes" at Staples for $4.99 or whatever, and you could send away to get the remaining two episodes (to wit, the whole game). That was a genius business model; even Doom was originally distributed this way ("Episode 1: Knee-Deep in the Dead"). But man, piracy would massacre that business model nowadays. But back in the day it made for great little games. They're on GOG; check them out if you haven't. Not Apogee, but great games of that model: Wolfenstein 3D (not a great game, aged like milk but historically important), I think Descent -- the GOG version lacks built-in support, and perhaps any support, for an Xbox controller; tgis was a major disappointment; be forewarned!), Commander Keen (three separate three-episode games), Jazz Jackrabbit 1 and 2, Duke Nukem 1 and 2. PC platformers don't get their due.