Yes, I know the category "Arcade - Boulder Dash" contains 1145 entries of which a majority is hacks. That leaves 2855 additional hacks and alternative versions of all games that are not Boulder Dashes.
Whether or not to count type-ins, user group games, other public domain items etc is a subject of matter. If you don't count C64 games that origin from user groups, you shall not count ditto Apple ][ games. Did the EG magazine only count mostly commercial software in their figure of 16000 titles?
How many unique games did Electronic Arts release for the Apple series as comparison, as you seem to suggest that 70 is a very low number? For that matter, Ocean has a little over 90 games, Activision some 80, Mastertronic at least 120-130, a little over 10 games from System 3 and so on.
Anyway, it should not really be a contest who's got the longest **** but how many of those 1000, 5000, 10000, 15000, 20000 titles are recorded, ideally archived as well.