Yeah, it all depends on the ramp. It's nice of all these folks who have never seen your ramp guarantee you'll be fine. Up here in slimy, slippery, mossy Oregon it's pretty common to see a 2WD get stuck on the ramp. Luckily, there's usually someone with a 4WD to unhook and drop his trailer and pull you out. Worst you'll face is 10 trucks deep in line glaring at you.
You'll likely be fine but it sure sucks to not be. This is the same question that regularly goes around RV boards. OP, you are obviously worried enough to ask the question so it just depends on your risk tolerance. I sold my boat years ago and only had it for a couple years so I really don't have that much experience but did use my 4WD a few times. Would I have been stuck w/o it? Not sure but I was really glad to have it. Pickups are just so light in the rear that, more than any other vehicle type, I couldn't imagine not having a 4X.