The Avengers cartoon isn't that bad, in my opinion. It starts off pretty slowly, but by the end, I was really excited for the second season. In regards to your initial question, I think I prefer something to look pretty bad or mediocre and then pleasantly surprise me. That's why I try not to overhype movies/games/TV shows anymore because if they suck, then I go into a spiral of depression. It's not nice.
I thought Avengers EMH was pretty fantastic personally but I'd rather have it be almost good rather than a complete failure. A complete failure has nothing to redeem it. If you have some seeds of goodness they can grow.
That said I still hate the Avengers EMH theme song.
I don't know, I dumped Avengers EMH pretty early because it seemed to be more intent on playing the long game and doling out the occasional easter egg for long-time fans than actually providing 22 minutes of consistent entertainment every episode. The boys were bored out of their minds by the first four episodes and they're far more interested in watching Regular Show or old episodes of Batman TAS on Hub than watching it again (and they both loved the Captain America movie and are pumped for Avengers).