now *this* is an insane question...
i went through my database and just did a cursory glance coming up with these, which is by no means an exhaustive list (all CDs):
- alio die: incl. collabs, 31+
- asmus tietchens: 38+
- atom heart: incl. collabs, 35+
- bill laswell: 40+
- brian eno: 30+
- cabaret voltaire: complete catalog, incl. all aliases/solo/collabs, 70+
- chris & cosey: 30+
- conrad schnitzler: 35+
- controlled bleeding: 15
- future sound of london: 20
- harold budd: incl. collabs, 20+
- ian boddy: entire catalog, incl. collabs, 28+
- kim cascone: incl. collabs, aliases: 30+
- klaus schulze: entire catalog, 60+
- mathias grassow: incl. collabs, 30+
- nurse with wound: 45+
- ontayso: 44+
- oophoi: 30+
- radio massacre international: entire catalog, 36 discs
- rapoon: entire catalog, incl. collabs, 40+
- richard bone: 20
- robert rich: 30+
- roedelius, moebius, cluster: 50+
- steve roach: entire catalog incl. collaborative projects, 85+
- tangerine dream: 66
- the orb: 21
- vidna obmana: 30+
- zoviet france: entire catalog incl. collabs, 25+
the winner is probably namlook/fax cds, of which i have well over 117 namlook, and another 70+ fax discs.
and mind you, this is just culled from the electronic portion of my library - doesn't count jazz or rock, such as complete catalogs of miles davis, ozric tentacles, weather report, wire, genesis, yes, bowie, billy cobham, john mclaughlin/mahavishnu, lee morgan, freddie hubbard, allan holdsworth, just about all pat metheny, good chunk of king crimson, etc.
not sure of the efficacy of this question. i don't consider myself a completist per se, except that if i like a certain artist/group well enough i generally have acquired all of what they've done (or what is available), but this isn't a hard and fast rule. some artists have released what i thought were terrible records that i never bothered with when they were released on CD, or just didn't like enough to want to own. some artists are just incredibly prolific, or have been around for some time (t.d., schulze, roach, metheny, etc.) and have vast back catalogs.
and, in many cases, it's not the quantity per se but the quality...