I don't know which to buy. To make things easier I'll give some information.
1) I don't play games online. This has to do with 3 things: I have two people always pirating 24/7 so my ping would be in the hundreds (unplayable mess). From my previous online experience it full of mostly cheaters, kids, and no-lifers.
2) I already have a Blu-Ray player and don't need all those streaming services or any of that other stuff. I just want my console to play games, that's it.
3) I play a lot of sports games. PS3 takes the edge here, right? If only for The Show and Hot Shots Golf.
4) I play a lot of RPGs. More-so JRPGs than WRPGs. Again I would assume the PS3 has the advantage, but I'm not sure if Sony is still the king for JRPGs like it was with the PS2 and PSX. I do enjoy WRPGs like Elder Scrolls, Fable, Dragon's Age, Fallout, etc.
5) I like FPS. This would point toward the 360, but since I don't play online, I'm not sure. I've heard that most FPS have little, if any, single-player story modes. If they do they're extremely short. I could be wrong though. Paying 60$ for a few hours of campaign is pointless.
6) I like the 360 controller. I own an Xbox and have a 360 controller for my PC so I'm already adapt at using it. Haven't used a Playstation controller since the PSX.
7) I can play some games on my PC. So get rid of games like L4D, Elder Scrolls 4, Borderlands 1, MLB 2K, etc. Just can't play the most recent ones like Borderlands 2, NBA 2K, Elder Scrolls 5, Mass Effect games, etc.
Judging from what you said, I think a PS3 might be a better choice for you. The 360's main advantages are better online support (which you have to pay for) and a few exclusive titles (mostly shooters like Gears of War and Halo, though they do have a few non shooter exclusives like Fable).
JRPGs are still mostly on the PS3. The XBox 360 has not sold well in Japan, as shooter games and western RPGs don't sell well over there. Japanese developers have thus not supported the 360 all that well. Most JRPGs are PS3 exclusive, or if they are on the 360, the 360 version is usually inferior to the PS3 version.
If you like Bethesda games, I would recommend you play them on PC instead of PS3 though. Bethesda games like Fallout and Elder Scrolls don't work as well on the PS3. The PS3 version of Skyrim is one giant disaster because Bethesda can't work around the PS3's memory limitations.
You're right about the shooters having short SP campaigns. Ever since Call of Duty 4 came out and became a smash hit that everyone felt they needed to copy, single player campaigns in FPS games have gone down the tubes. They are more or less treated as a feature that is tacked on out of obligation. Publishers feel if they drop the single player campaign, they can't charge full price for their games without getting lambasted by critics. As such, SP campaigns are given the minimum amount of effort to fill in the checkbox that says the game has single player. The average campaign length is 4 hours now for FPS games, though some games will go up to 6 or 8 hours if you're lucky eg. Crysis 2 and Metro 2033. If you want to play the current shooters for single player only, you might as well rent them for the weekend (assuming you still have a video store in your area).