One of the lessons video games (and the Scary Movie franchise) is late to coming to is that it's not enough to just reference something; reference isn't parody, and by itself it's not entertaining. It's also not enough to point out the stale cliches of other games while repeating them themselves: this doesn't make them any more fun to play or acceptable. Deadpool illustrates these lessons over and over again in the most cringe-worthy ways, and then punctuates them with boring, repetitive gameplay.
That's not to say that there aren't some jokes that land. On average, about a quarter or so of the written dialogue and scenarios in Deadpool are genuinely funny or interesting. Unfortunately, the majority of the rest is tired, lame, or feels so throwaway and pointless we were left baffled as to why it was included at all. Maybe in some dark, grungy pocket of the earth there's an audience that still giggles every time the word "crotch" is uttered, but we're not it.
"Boredom: the desire for desires"
That said, if the action were crisp, entertaining, or in any way unique, a lot of the sub par dialogue and lackluster story could be forgiven (a story which, true to Deadpool's infamous fourth wall breaking shenanigans, involves the augmented mercenary raiding High Moon Studios to force them to make a game about him). Instead the action is bland and lifeless third-person combat we've seen done much better in countless other games.
Strapped on to the very vanilla combat is an upgrade system with which Deadpool can improve his weapons, or purchase new ones. The main problem with the upgrade system is that, almost universally, the best part about a new weapon is how it looks on the icon in the upgrade tree. Actually wielding the new weapons, like a shotgun or dual hammers, feels almost identical to using the default weapons, or in some cases actually less satisfying.
So much less fun than it looks
The levels are flat and boring, and the enemies you battle your way through are almost all indistinguishable from each other. The game also features a lock-on targeting system for the shooting that has the dual effect of making the shooting really easy and very boring, in that it doesn't require any skill whatsoever or challenge you on any level.
If either end of the package had been exceptional, if the writing had been consistently clever and amusing, or if the gameplay had been consistently fun, the whole could have been salvaged. Sadly, both end up falling well short of the requisite level of quality, and the final product is exceedingly tedious and grates on both nerves and patience.