Well, the definition of Anti-hero is going to vary depending on who is reading the question, so it's a very subjective opinion. I see two possible definitions of an anti-hero, encompassing "good guys" who don't necessarily act like a typical super hero (ie, they are cooler) or it could also mean a genuine "bad guy" who is able to get me to either like him or root for him somehow.
Definition 1: the good guy who doesn't act like a good guy: I would consider Wolverine a legitimate anti-hero, in that while he is one of the good guys, he rarely acts like it. He enjoys violence, will definitely kill you if the situation warrants it, curses, drinks, enjoys most of the things the goody goody two shoes variety of hero would be revolted at. Using the X-Men universe as an example, if Cyclops is the representative goody two shoes variety hero, the squeaky clean type who parents would want their daughters to date, Wolverine would not fit in with that definition of hero, yet he is a hero. He is a good guy. Mostly. So, if you define anti-hero simply as a hero that doesn't fit at all into the standard hero mode, ie he doesn't act all noble and high and mighty all the time, then Wolverine definitely fits the definition.
Definition 2: The sympathetic bad guy. Again, staying in the X-Men world, There are times when I have a hard time rooting against Magneto. His methods are sometimes appalling, but, is his purpose? His actions clearly mark him as a villain, he would easily be considered a terrorist. Yet, what is he trying to do? Is he trying to conquer the world, just because conquering the world sounds like fun? NO. He does it to win mutant rights. He more or less has the exact same goals as Charles Xavier, but his methods are very different. There isn't anything particularly wrong with the idea of ensuring that mutants aren't treated as second class citizens, and given his past as a persecuted Jew in Nazi Germany, it is certainly understandable why he would be far more skeptical of humans and mutants living peacefully together than Professor X does.
Were he a true villain, Charles Xavier would not try so hard to "redeem" his friend. I think on some level at least, Charles recognizes that Magneto is not 100% wrong. So, he could be considered an anti-hero too, as a bad guy that evokes some amount of sympathy. If a few things different occurred in his life, that gave him the ability to put aside his skepticism, Magneto could have been the greatest X-Man ever. Without the psychological traumatization that his childhood gave him, Magneto could easily have ended up a hero. I think deep down even he understands that. It's why he sometimes puts aside his differences with the X-Men and aides them. He gets to temporarily explore how his life could have been different. Hell, he even lead the X-Men for a while. He could be an anti-hero too, rather than a true villain.