A unique concept hits a unique market which leads to a unique and memorable experience.
Bear in mind the fact that 2K has been making games of separate genres for some time now. Bioshock for your FPS feel, and Oblivion for your RPG. Now Borderlands steps up as a RPS (role playing shooter for those who do not know) and really nailed the concept. I, myself, would not play this game alone because I made and oath to only play it with friends since I heard that it is way better with you buddies. They were right. Within the first weekend I played it with my friend, I racked up over 20 hours worth of game time in 3 days. It really is that addictive.
The game play may look as main-stream as any other FPS, but when you play it, you realize how much more fun it is than a standard FPS. The weapon selection is really much to credit for that. From using sniper rifles that explode your enemies heads, to shooting rocket launching shotguns, Borderlands offers unlimited choices. You will never see yourself using the same weapon as you friends. The leveling system is also tight and rewarding. Incorporating a tight attribute system, Borderlands gives the player the ability to level up their character to their playing style. With other bonuses such as Artifacts and Class Mods, Borderlands rewards gamers with a great possibility to make a character that you can really see putting 40+ hours into.
Graphics and story will go into the same section here, because there really is not much to mention about the story. It really is almost non-existent, and from what I have heard, the ending is quite disappointing. You are a Mercenary in search of a secret Alien Vault containing epic loot. And that is pretty much that. Very little character portrayal or depth is where the game really fell short for me, and for having a game made out of the same studio as Bioshock, very disappointed. The graphics on the other hand, are refreshing. It is great to know that game designers can not make the most realistic looking game, but still have a great looking game. The cell-shaded style sucks you into what world Pandora is and gets you to appreciate the effort put into how the game looks and feels, which is nothing short of incredible.
The bottom line is, Borderlands is worth the buy, and since I bought it while it was on sale for $40, I feel like my investment went into a great game. 2K makes great games, and Borderlands deserves mentions as one of their most re-playable games to date. If you can get a group of 3 guys to shoot-up Pandora with you, I strongly encourage to play with them rather than by yourself.