It also depend, I love 12-13 or 25-26 (if is a really good anime) episodes....but I always feel empty when a really good show end T^T...
Or when a short anime end with a super crappy ending or end without even completing the story (mahou sensou, one of the new anime that didn't even finish or announce a S2...just hated this kind of ending)
But if it come to my favorite anime and stuff, I will wish a 50 episodes long without cutting to S1 and S2, like the new Fate/Stay Night 2014 coming out, I'm hoping it wont cut into season like F/Z and making all their fan wait so badly for S2, since they already waited so badly for a remake <3 (Still hoping is HF's route, but with the trailer I don't think so anymore...).