Hi Kayvan - thanks for asking! There are no rules here other than "don't go crazy". 1 - 10 entries sounds reasonable. 50+ and I'd be thinking there's some automation, procedural generation, and / or cheating going on ;)
Just as an FYI, people have come up with fun ways to work in multiple games into the same entry e.g. http://js13kgames.com/entries/26-games-in-1.
Good luck!