I definitely think what defines so bad it's good can be subjective. For some, it's really fun games that are obscure, weird, bad art... others, it's due to the terrible glitches that don't ruin the game but make it better... it can be for the sheer spectacle of the plot and objectives which make you go "what the hell...?", it can be for cheesy voice acting, the obvious knock-offing of a popular franchise, or the fact the game seemed to be reaching to be something more (and maybe even an excellent concept) but misses its target xD
The jam has certainly spawned a lot of games covering almost all these aspects, I think. The important core of the jam I think is the fun factor, how much you enjoyed it for all the wrong reasons and replayability. Is it so bad... it's good enough that you'd dare rank it amongst your favourite games of all time, and not for the fact it's a "good" game but because it is essentially "bad" and that's why you love it xD