This role reversal is created by the character of Deadpool, who is one of the most self-aware characters of any medium in which he exists. Constantly breaking the fourth wall, he speaks directly to the reader -- in this case, the player -- while the other characters chalk up his behaviour as just another manifestation of his unstable frame of mind.
And his constant chatter never stops! While the player primarily interacts with Deadpool's ego, his id and superego lend two additional personalities (with voices to match) all having a three way conversation while at the same time addressing the player and the supporting cast of characters including the baddies, the X-Men AND the game designer whom he berates from time to time about the quality (or lack thereof) of his game design.
There's our first premise right there: the player is playing a game commissioned by Deadpool, designed by an unwilling game designer with little budget ('cos his mentally unsound employer has no money to put into game development) while the point of the game is to complete an assassination contract so that Deadpool can be paid some money so that he can pay the game designer to come up with a better job of designing a game worthy of the Deadpool name. Wow, summarized in one sentence! Terrific!
Ok, that's the meta part of the game. The playable part is dead simple: help Deadpool kill lots of people -- sometimes in the goriest way possible; pick up buxom chicks (his people skills are zero, though, so this challenge is totally impossible); and if he's taken damage, stay alive long enough for his regenerative power to kick in. If he dies, he will scold the player for letting him down. Trust me, he will die. A lot. And then the player can continue the game from the last save point, and hopefully get better results, i.e., plot progression.
Here's a good time to present a parental advisory: D:TG is ridiculously violent. Deadpool is inhumanly proficient in both melee and gun fights. We may be used to enemies being gibbed in normal gameplay, but Deadpool's stealth attacks are horrifically vicious... yet so satisfying to pull off. It's also funny as while sneaking up on a poor, unsuspecting schlub, Deadpool will occasionally turn to look at the player with a finger to his lips, or use hand signals to indicate whether to advance or stop as he tracks the movements of his target for the optimal strike.
What I like about D:TG is that it is a comedic romp hosted by a nonsensical, sophomoric psycho who gets away with gaping plot holes; a tenuous grasp on reality; and shameless, self-aggrandizing narration. The game mechanics vary wildly, as random as the game's eponymous protagonist's state of mind, yet there is still some discernible method to the madness.
What I don't like is that there are too many buttons to mash, especially when I'm not playing with a console controller but a keyboard. Although I can map the keys to my preference, some key combinations are impossible to execute without temporarily losing control of the character. As the game progresses, more and more fighting combos are unlocked, but it still comes back to mashing the most accustomed set of buttons anyway. Dexterously uncoordinated, that's me.
Some people don't like the fact that completing the game doesn't take long, but I like short games 'cos I have a life.
D:TG is violently fun and relies a lot on cheap humour (including toilet humour and bad puns -- the first game objective is to "play with Deadpool's junk," hur, hur). Gameplay is not difficult (barring the number of buttons to keep track of) but does take time to figure out the right timing to balance kill efficiency with long-term survivability. However, after playing the game once through, there seems to be little incentive for replay. Maybe that's for the best. Summer vacation is over.