Ranked in these QuestionsQuestion Ranking
Pro Long history and strong community
Ludum Dare has been running since 2002, with tens of thousands of entrants at every level of proficiency. As an industry-wide event, participation carries a sense of being part of something, and there's no shortage of interest or discussion online.
Pro Other people actually play your game
Pro Chance to see developers writing code
Pro Most popular game jam of all them
Pro Theme Voting == FUN
The fact that everybody gets to VOTE for an entire week to generate a shortlist and final theme which is announced in real-time to great fanfare is half the fun. It draws you in, gives you ideas beforehand, and generates a conversation online in the days leading up to each wonderful #LD48.
It is like a drum roll that gets you excited.
Con Theme can be too specific
The themes can be too specific, which can limit the creative game ideas.