The first borderlands suffered from a terrible wow-esque (!) quest system that kept sending you back to the same areas repeatedly to complete missions. In the first 2/3rds of the game you basically had to acclimate yourself to this bleak world full of trash and white trash yokels in hockey masks trying to kill you. The latter half of the game plot actually focuses, provides a coherent story goal, and pits you against a clear enemy. It held up as a strong game when it took the time to focus like that.
This new one has the same quest style but with more interactivity, plus the missions are related to the central plot or its friends in some way or another. It's a shame they didn't improve it so you could have more than one mission active at once, but I consider it a minor nuisance. What really annoys me is the inventory system and equipping items. >:-|
But yes, it's meme heavy, tries too hard in some places to be funny, and can be repetitive. To me the game is challenging, plays along the same idea as diablo (get better loot) except in an absurd environment; it's only a step away from serious sam, except with a bigger budget and probably takes itself as seriously. Usually when I'm done with a session of that I'm literally brain-dead from all the explosions, flashy lights, and maneuvering I had to do along the way. I'd play this over a modern warfare game any day.