I like ambiguous endings, but not in terms of "who won" (which is a really bad method of grouping endings but whatever). If who won is ambiguous it usually strikes me more as "whoops we forgot to resolve the plot".
Bad and tragic endings are, in my experience, basically never done correctly even if they're fine in theory. To be continued is fine except when it's another case of "whoops we forgot to resolve the plot" or, even worse, "please buy the sequel to learn how the game actually ends".
So I guess I prefer good endings, though those are usually awful too.
tl;dr: the best ending is frequently when you just stop playing 85% of the way through and pretend everything resolved itself in a satisfying way.
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"The courtroom is the garden of holy judgment. Those with lechery in their hearts should leave this sanctuary at once!" ~Franziska von Karma