I don't think Man of Steel really counts as an introduction trailer. The original introduction trailer was what we got last year, and it was underwhelming.
On that note, I went back and watched the other three candidates. I think it's Thor 2. All were good trailers, but Iron Man 3 has some weird editing and confusion to it's trailer, plus it's kind of the cliche build up for a third entry in a superhero franchise. The Wolverine was cool, but it didn't quite make me forget that there was already a Wolverine movie and that had a good trailer...but ended up sucking. The Thor 2 trailer on the other hand is fresh out of the gate and looks to be taking a turn to be the kind of Thor movie that people want to see.
Even if I was counting the recent Man of Steel trailer I would still probably give it to Thor. Some of the CGI and shots in the Man of Steel trailer had me really worried.
Thor: The Dark World. There is just no contest there, as none of the other trailers came even close.
The Wolverine looked pretty terrible (and this is coming from someone who actually liked Origins)
Man of Steel looked decent in the newest trailer, but the other two were "meh." I really don't get what's so good about that second trailer.
Iron Man 3 looked incredible, but I still give an advantage to Thor.