No, the alien is the best. I just experienced the cheapest, most bullcrap thing ever. The alien's tail is absolutely balls off the wall stupid. If you hit anyone with it, it will stagger them and damage them so much that all you have to do is light melee 2 times and they die. Even cheesier is that one can tail whip a guy, then run behind him and do a finishing move. It was absolutely stupid. Any sort of melee combat with this guy playing the alien and you lost every time, all the time. If he couldn't hit you with his tail, he'd strafe around you spamming E until he got the finishing move. So retarded.
What makes it even worse is the lockon. Even if you backpedal 20 feet you'll still be struck by the tail. I'm
pretty sure that meleeing as the Marine stuns enemies though (I asked people after I melee'd them and those that answered said that it seemed like it did), so I think you have to learn how to time close-quarters combat, i.e. shoot them until they're close, melee, backpedal, shoot. It's hard to figure it out with the matchmaking system though, wish I could just find a place to play with friends to try stuff out.