Borderlands 1 is free on PS+ right now, however before you tell me that the game was way better back then, I can say that I tried it back then too.
As a matter of fact, I bought the game when it came out. Reached all the way to lvl 45 Mordecai. Maybe it is because I mostly played it offline rather than online (because it had some issues that I disliked when playing coop online), however I found the game to be extremely repetitive.
My problem with online coop is that people hoard treasure boxes and grab everything, even if they don't need it. And the core gameplay is pretty standard too. Is just shoot, shoot and shoot.
That doesn't mean that I hate online components. I loved Rainbow Six Vegas coop. It was amazing. So, like I said before, I can't find what's so fun about the Borderland games.