Crazy, with fo3 and di in your list, I figured you of all people would have liked it.
Have you tried the second one? It's a lot better in certain aspects than the first one.
Also, I saw skyrim missing from your list! You have to try it out! I would play it with all the DLC that is available at first. Then try a second+ go around with mods.
The mods for skyrim make it very, very awesome.
The borderlands games are first person shooter RPGs that are cell-shaded.
They have a lot of humor, sometimes dark, mixed in.
They are like the diablo games with loot. Lots of loot, the different colors for different levels, with varying stats.
Your character has many levels to gain and skill trees. Inventory system, ect...
Here's a youtube vid of BL2 to show you a little about it, skip to around 7:00 for some fighting and them some hilarity:
http://www.youtube.com/watch?v=At0HioLQz3Q