Fallout 3 is somewhat similar (FPS with pseudo-role playing features) but has only one character that more or less will play the same each time you play the game after a certain point. Only some of the enemies respawn (with very limited scaling), however, and the amount of gear is far less as well.
EDIT---I missed the part about you and a friend. FO3 is single player only.
diablo_power50 posted... I'm searching for a coop game
That's the thing: co op is a scarce thing right now, especially for FPS games. That why the Borderlands devs were so adamant about the game having online co op and split screen co op (I'm referring to the console version.)
Portal 2 is a big co op game. --- Two Pyramid Heads walk into a bar. There were no survivors.
Serious Sam 3 is an FPS with 16-player online co-op and 4-player splitscreen co-op (including the PC version), but it doesn't have the levelling up and loot elements of Borderlands. There's also Payday: The Heist and Syndicate, but those don't have as much content as Borderlands. There's Left 4 Dead 2, which again doesn't have the RPG stuff. Bulletstorm has a quite cool horde mode co-op, but doesn't have campaign co-op like Borderlands. --- John Magnum Master of Subtlety
Hellgate: London is probably the closest thing out there. It uses first person unless you are using melee weapons and it has the same sort of Diablo style skill system and loot system.
It is also currently free to play. It has the Korean style cash shop, but you don't really need anything out of it as far as I've seen.
The only problem is that it got butchered when they made the free to play version. For some bizarre reason, the Korean company that turned it into a free to play game decided that instead of using any of the English text from the original release of the game, they would translate it into Korean and then translate it back into English. I haven't played all the way through that version, but it looks like they completely cut out the most important NPC in the entire game. The story makes literally no sense.