To be fair, that doesn't actually limit the number all that much:
http://tvtropes.org/pmwiki/pmwiki.php/Horrible/VideoGameGene...
And much of:
http://tvtropes.org/pmwiki/pmwiki.php/Horrible/VideoGamesOth...
And everything on Hardcore Gaming 101's Weekly Kusoge series here:
http://www.hardcoregaming101.net/kusoge/kusoge.htm
There's also the fact a lot of games are distributed pretty well (and sometimes even sold), legality be damned. Is there any more legitimacy to a bad (and likely illegal) app store game featuring characters from Mario or Pokemon than a game mod or fan game featuring the same thing? People sold Doom Wad collections in boxes in shops at one point, does that count?
Even assuming only legal retail games, there's an awful lot of somewhat obscure shovelware that could fill up an entire (very long) list. Like the tons of PS2 and Wii shovelware (the latter's games were often ported from the former) by companies like Data Design and Phoenix Games.
Like:
https://www.youtube.com/watch?v=UF8QzQp57oI
https://www.youtube.com/watch?v=Pk8qbSISQI4
A worst game ever list would be incredibly hard to make to any decent degree, simply because you have so many possible choices to include on it, especially if you go looking outside the most popular titles.