A question for Borderlands Players...

[Proxy-Pie]

It's a actually a "Pre-Sequel", so it's more or less Borderlands 1.5.
I'd play the original, then the Pre-Sequel (I guess, I haven't played it yet as you can imagine :P) and then 2.
The Multiplayer is basically co-op. there's dueling too, so it's fun as heck with friends!