I don't see what all this negativity is about...
*sigh*
All right, let's start this.
First off, the premise: You are the player. You are not Deadpool, you -are- the player. If you didn't know this yet, let me spill the beans: the game relies on meta-humor to an almost frightening degree. Deadpool doesn't as much break the fourth wall as hops on top of it, does a tap dance and then gleefully shits all over it. You are just following him around while he does so, and honestly, if you have a knack for self-referential humor and meta-jokes, this game is a goldmine of them and will make you laugh your ass off.
Now, for the technical details, the game is reasonably good. The graphics are not outstanding but are not bad either. The cutscenes are extremely imaginative if a little whiplash-inducing at times, generally well-animated and the voice-acting is top-notch. Sadly the same can not be said about the in-game animation. Deadpool's moves have woefully few frames, and special moves like wall-jumping and the like are especially bad. The action is also waaaaaay too fast in the bad sense, when even an elaborate sword-play combo is over so fast you have no time to appreciate it, and there are also some camera-issues in close quarters, though I decided to cut the game some slack in that regard as I have yet to see a frantic third person perspective hack-n-slash game with perfect camera controls.
For the gameplay, I don't see what most people are complaining about. Yes, the combat is repetitive, like in all hack-n-slash games... unless you actually do what the developers want you to do and use the combo system.
In short, every hit you do adds to the combo-meter on the upper right, and each enemy killed gives you bonus upgrade points in the lower right. Get hit, and you lose both of those. Don't get hit, skillfully dodge your way through your opponents, use your appropriate weapons to rack up a huge combo bonus and finish them off with a weapon with a bonus to upgrade point gain, and at the end of the fight the two numbers get multiplied together and you get large amounts of upgrade points you can use to buy some badass equipment and upgrades to make the combat easier and fun.
Yes, you can get through 90% of the battles with the same stock clone enemies by simply button smashing, but then you have no right to complain about the gameplay mechanics, as you are not actually using them.
Aside of melee, Deadpool has a small assortment of guns as well. Sadly they are pretty weirdly balanced, as some enemies take dozens of shots to take down, while the next enemy of the same type might fall in one lucky shot...
Speaking of guns and aiming, the control scheme of the game for the PC is the most backwards thing I have ever seen. I practically had to spend about half an hour repeatedly re-mapping the keys to comfortable positions (made even worse by the fact that the game only accepts a limited number of keys and that you cannot map an action to a button already taken by another action, so sometimes it was like a puzzle-game where I had to move key-bindings to random keys before I could bind them to the button I actually wanted to... -.-). That said, once I mapped things out properly, I never had any control issues.
The game also offers a large amount of gameplay variety. Though each of those little sections felt like a little tagged on, I think we should never complain about variety in our modern brow-gray-chest-high-walls-shooter days of gaming.
Now, for the story, there really isn't much to talk about. It's Deadpool getting dragged into a huge incident he doesn't even know about since he is too frantic to listen to any of the plot dumps and just runs around killing things at his own amusement. Really, the plot is not at all that important, since it is all just an excuse to have fun.
And here is the crux of my argument: This game is FUN. It's not about gameplay or story, it's about getting into the head of Deadpool during one of his manic adventures and have insane amounts of fun while doing so. The entire game, gameplay and story included, is just a huge vehicle designed to deliver meta-jokes (about both comics and video-games) and crazy non-sequitur humor by the truckload. This is not an action game. This is a comedy game (whether that genre even exists or not) masquerading as an action game. Sure, it is crass and juvenile and crazy, but it is Deadpool! Complaining about those things is like complaining about how the sea is wet!
In conclusion, I would say this was a pretty dang good game with some glaring but not deal-breaking flaws. Not a classic, not one that I would recommend for everyone, but it was certainly an extremely fun (if at times a little tiresome) experience that should be judged for what it actually is: a piece of absurd meta-comedy dressed in action-game clothes.