When I got back into cycling, I switched to a hybrid bike. I ride a Trek FX 2 now and find the geometry on the hybrid very comfortable. In the old days I had a 10 speed Raleigh with drop bars.

You can always go to LBS and test ride a couple of different style of bikes to see which seem to fit you best now. A lot depends on the type biking you plan to get back into. There's no "right" answer, lol.

Bottom line, it will take a bit of time to get your biking legs (butt) back. It will be a struggle but you'll get there if you keep at it.