Computers for the most part aren't worth getting. A lot of them had a bare minimum of games, and trying to find and figure out Japanese PC variants would take you a few billion years. Okay, maybe not that bad. Keep in mind that not all of them are emulated...just the more well known ones are. (more well known in japan!)
Computers for me is definitely a case of 'dont buy it if you wont use it'. I would buy say, a SC-3000/SG-1000 (in fact i had a datasette for one once - I donated it to Zoop, in the hope that it may improve emulation quality for him...but I think it turned out to be dead, unfortunately), but I would not buy a PC-88 or something because while there's good games, there's only a bare minimum of them. Considering the amount of space it takes up and the amount of space I have, not to mention the amount of other equally good or much better games I have, it's just illogical. I stick mostly to the major stuff. Computers I would buy (including ones I have) are Commodore Vic20/64/128/+4/16/Amiga (but not PETs), Amstrad CPC's, ZX Spectrums (mine has no power cables I think? Does it work even? I got a ton of games at an auction...), MSX and its variants, um...maybe a BBC or something? Maybe the Atari computers? I mentioned the Sga ones already, um...there's probably more but I can't think of it. Console-wise, I'd buy virtually anything on the condition it is a console (ie not N-Gage or handheld LCD games).
Quite often I find myself giving tips on locations of good stuff to other collectors, if I don't want the item myself...and occasionally if I double up for some reason (usually when I don't know if I have some sports game, or bundles of games, or simply because the game is impossible to pass by), I'll give away or trade that to one of them also. I'd rather see the games go to someone I know will appreciate them than one of those 'must get everything' types...