I have absolutely no idea how you keep coming to the conclusion that people are going to think X-Men other than that it has the Marvel brand attached and its a team film. By that logic then every team film should be associated with the X-Men, especially Avengers since it's Marvel branded too. :/
And as I said before, GL is not a good comparison because this movie IS NOTHING LIKE IT, and it won't look anything like it. This isn't a hard concept to grasp, it's completely different. Just because they have the superhero tag doesn't mean they're similar...and the Guardians are "superhero" in name and relation to Marvel only.
Star Trek is at least a palpable comparison that doesn't sound off base, but it's still not a good comparison because, again, this movie will not be like it. The only apt comparisons for this movie are Star Wars due to the pulp space opera element and Galaxy Quest as its a space action comedy...and even the comedies are sort of two different brands because this will be much more sultry and as James Gunn's humor is more black comedy than pure slapstick like Galaxy Quest's.
Simply put, there are no good comparisons for this movie, it's unprecedented on multiple levels. Star Trek's, Green Lantern's, First Class's, and even Star Wars' performances at the box office are not good indicators for this because it's inherently different from every single one of them. And if you wanted to simply summarize the movie up into something the general audience would associate it with based on trailers, it won't be Green Lantern or First Class, it will be Star Wars and Galaxy Quest, and that's how Marvel will play up the trailers.