For the size question, my games/emulator directory is about 21.5GB, with 16.6 devoted to "arcade". This includes emus/roms/front ends/utilities. However, that does not include my PC games.
As for emus, I mainly use
FCE Ultra (NES)
gensFE (Genesis)
ZSNESW (SNES)
Project64 (n64)
Visual Pinball
Mess (for atari2600, but looking at z26)
Zinc (for Street Fighter EX series & Strider2...hum, has MAME made any progress with these titles? BTW, Zinc actually uses your video card and 3d plugins, making for a better game over mame...it's not "pure emulation" if your into that...)
Also have Visual boy advance, chankast, epsxe, and stepmania, but I hardly use these.
Cab friendly emu's can be found here:
http://www.screenshotarchive.com/downloads_emus.htmMessing around with various jukebox progies to find a cool one...currently running Arcade Jukebox 8. DigitalJukeBox was also nice with more features.
PC Games I run:
Need For Speed Underground (I actually got pretty good using the joystick instead of a wheel...it works)
Armagetron (lightcycle)
GLtron (lightcycle)
DXBall2 (breakout)
Golden Tee Golf
Hamsterball (monkeyball)
LaserAge (shump, gallery)
Microsoft Pinball Arcade
MutantStorm (only the demo, but still awesome robotron game)
neverball (monkeyball)
neverputt (minigolf)
Ricochet Lost Worlds (breakout)
Star Monkey (shump)
Ultra Assault (shump)
Art is Dead (gun)
Some good PC games are listed here:
http://www.timoproductions.com/arcade/pcarcadegames.htmlwhich was born out of this PC game listing thread thread:
http://www.arcadecontrols.org/yabbse/index.php?board=3;action=display;threadid=7479Game On!