My 'currently in stock' systems:
Atari 2600
Atari Jaguar
BBC Micro Model B
Commodore 64C
Commodore Amiga 600
Microsoft XBOX
Toshiba MSX
NEC PC-Engine CoreGrafx
Nintendo 64
Nintendo Gameboy Advance SP
Nintendo NES
Nintendo SNES
Nintendo Super Famicom
Nintendo Wii
Philips CD-i
Prinztronic Tournament 6 (Pong system)
Sega Dreamcast
Sega Master System 2
Sega Megadrive 1
Sega Megadrive 2
Sega Saturn (PAL)
Sega Saturn (NTSC Japanese white version)
SNK Neo Geo AES
SNK Neo Geo Pocket Colour
Sony Playstation 2
Vectrex
My 'coming soon' systems:
Funtech Super A'Can (Taiwanese 16-bit system)
Sharp Famicom Twin (the bright red version!)
Oh, and I also have a MAME cabinet (converted from JAMMA) and a Taito Ground Effects arcade cabinet that is awaiting conversion to a MAME driving cab. And a bunch of those plug and play TV games.
Games-wise I am fast approaching a grand total of 1000 games across all the above systems. I particularly like Japanese weirdness, shmups and platformers and my speciality is anything to do with Bubble Bobble, as you can see on the following link if you wish:
http://gameaddict.blog.co.uk/2008/09/26/now-it-is-beginning-of-a-fantastic-story-4781988