If you want a list of games, then you get to define "game" first
Redump for disc-based consoles (and No-Intro for rom based ones) is a nice place to go if you want a list of
all dumped commercial releases - the lists are in clrmamepro format though (xml based, if you feed that program an empty folder it will generate a text files with the missing games - therefore, all of them, or there may be nicer frontends for those lists)
Gamefaqs may be an option, though you would need to copy/paste together 27 pages (one for each initial)
If unlicensed titles are to be considered (the first couple of sources include some but the criteria is fairly arbitrary and variable over time), all bets are off
