Not counting Marvel, here's the list of companies I included (note: some like Stanmor include ALL the various permutations in that line) and the numbers I used:
Accepted - 9
Ace - 701
ACG - ~853
Argo - 30
Avon - 407
Blackerby - 4
Cambridge House - 8
Catechetical Guild - ~150
Centaur - 229
Civil Service - 10
Columbia - 150
Comic Media... - 97
Cross - 42
Croydon - 10
David McKay - 536
Dearfield - 44
Don Fortune/Vic Verity - 13
Dougherty - 6
DS - 72
EC - 399
Eisner - 2
Famous Funnies - 503
Farrell... - 375
Fawcett - 2156
Fiction House - 831
Fox - 684
Gilberton ~200
Green ~50
Chesler - 80
Harvey - 1246
Hawley - 6
Hillman - 413
Holyoke - 177
Kirby - 16
Lafayette - 10
Lasalle - 3
Leffingwell - 6
Lev Gleason - 708
Mainline - 17
ME - ~425
Misc... (I'll have to break this out later) ~525
MLJ - 263 (not counting Archie)
MS - 5
Nationwide - ~30
Nugent - 5
Novelty - 331
Orbit - 161
Parents - 313
Pflaum - ~150
PL - 20
Prize - ~600
Quality - 1698
Rural Home - 30
Spark - 10
Spotlight - 8
Standard - 1108
Stanmor... - 158
Star - 280
Sterling - 18
St. John - 900
Story - 139
Street & Smith - 357
Superior - 188
Timor - 13
Toby - 296
Trojan - 120
United - 596
Victory - 6
W.H. Wise - 33
Youthful - 82
Ziff-Davis - 208
= ~20,295
add
Charlton - ~596
Archie - ~464
Comic Magazines/Ultem - 63
subtract
ACG - -100
= ~21,318
add DC - 3,585 (thanks to Mike Voiles)
add Dell - 3,799 (thanks to Dell4c on GACUK)
add Timely/Atlas - 3,456
for a GRAND TOTAL of: ~32,158
All the hard work was done by Dan Stevenson about 25 years ago and I've just transcribed some old notes of his. He probably has a MUCH more accurate count by now. Hope that helps to clarify things.
Peace, Jim (|:{>