Although i have hardly anytime played on this on pc, i have 1200+ hours on console, so i can give a fair review for this game.
Borderlands 2 is one of my favorite games of all time and my favorite co-op shooter. However i will give the fairest review to this game, so ill exclude my bias opinions.

Artstyle/graphics
If you have seen gameplay/pictures of the borderland games, you will notice the unique artstyle to the game. This is cel shaded-style. This gives the game a more unique feel and it also suits the gamestyle, as its a not so serious game.

GAMEPLAY
The gameplay is excellent.I don't want to get into detail with the story, just to evade accidental spoilers, but you don't have to play the other borderlands to understand the story, the story is explained throughout the game, the story is intriguing and very FUN! The rng system allows for TONS of weapons to be looted by you. According to Gearbox Software, there are over 17,750,000 different variations of weapons in Borderlands 2. Borderlands 2 uses a procedural process to generate its various guns in certain classes, such as handguns, shotguns, assault rifles, sniper rifles, and more, but with many variations of firing speed, reload speed, damage type and more. This means every gun is unique. However as you level up you will see that less guns become as valuable to use as they are outdamaged by many weapons. *cough* unkempt Harold *cough* This is because the game gets alot harder once you've beaten it. There is a mode called true vault hunter mode which includes the same story but with higher level and stronger enemies, but this allows you to progress your character more, allowing you to level up more and find better weapons. To level past 50 you will have to purchase some dlc, however it is not needed to enjoy the game.

PROS

The characters are hilarious and well developed. (E.G. CL4P-TP and handsome jack)
The huge variety of weapons.
The classes and abilities are very unique.
The replayability.
CO-OP!
The story.
Endless farming and grinding for exp and weapons.
The Easter eggs in this game are too funny!



CONS

Once you fully max your character (level 72 op8) there isn't many guns that will benefit you, as the dominant guns are literally the combo, grog and Harold, or bee shield and sand hawk, however there is many characters to replay as and different builds to make certain weapons highly suitable to your build.


TL;DR
This game is fantastic! The loot, the story, the characters, the Easter eggs, the co-op, the gameplay everything about it makes it an amazing game. If you haven't already got this game, it is definitelyworth it's money.