Naturally they aren't mentioning TDK or anything, but some things get stucked in our collective memories - "Citzen Kane" being the best movie of all time, "Apocalypse Now" being the best Vietnam war movie of all time and TDK being the best CBM of all time. Some agree with that notion and some disagree, but in general people are extra careful to challenge the status-quo.
Well, yeah, since the majority of people consider TDK to be the best comic book movie, I'm sure a lot of critics are going to be comparing X-Men: First Class to it. Heck, I'm going to be comparing X-Men: First Class to it. There's nothing wrong with that. Even though small minorities may disagree on the quality, as each comic book movie raises the bar, so should other comic book movies be compared to it. That's the nature of the beast. Even in the Academy Awards, they take 5 good films of extremely different genres and compare them, trying to see which one they deem to be the best.
People do that all the time. This is the general consensus I hear from the average Joe. "I like The Incredible Hulk better than the first one", "Thor was better than Iron Man 2, but not as good as Iron Man", "All the X-Men movies are good" (surprisingly), "Spider-Man is awesome", "Batman Begins is on the same level as Iron Man", "The Dark Knight is the best CBM" etc.
Moviegoers compare supehero movies probably more than any other genre of film. That's because, until recently, an upsurge in quality made superhero films "event films" and everybody was wondering which would be the best. I remember frequent conversations between people who weren't comic book fans about whether the X-Men trilogy was as good as the Spider-Man trilogy, whether Daredevil would be as good as Spider-Man, what in the world was wrong with The Hulk and why it wasn't like Spider-Man, how Batman Begins blindsided them with how good it was, how Superman Returns was boring and Spider-Man 3 was too campy, how Iron Man was the best CBM since Batman Begins, how The Dark Knight was amazing, how Iron Man 2 wasn't as good as the first. Right now the big thing on the mind of the people I've talked to is the whole Avengers setup. Even now they're expressing trepidation about the Spider-Man reboot and looking forward to TDKR, but they're excited about seeing different superheroes onscreen.
These are not really opinions that I share, but they are general opinions. You best believe that when X-Men: First Class, Green Lantern, and Captain America are released, there will be reviews comparing them to all manner of superhero films (how they're better than abominations like Catwoman and Elektra, how they compare to benchmarks like Iron Man or TDK etc.). So, in my mind, it's best to get used to the idea of X-Men: First Class being compared to what the general audience feels. I for one like such comparisons because it gives me an idea of what to expect from the movie.