Most of my time to date is in Robinson products, and they're not bad ships. Sure, the R-22 isn't the most ideal trainer... I think that award would have to go to the TH-55/269/300. But the R-22 can be a sporty, cheap machine and it's definitely got its advantages. I think the R-44 Raven II, as someone previously said, is the best thing to happen to Robinson ever. It's a blast to fly. I'm not incredibly experienced... only 220 hours total, but even I've managed to fly it from sea-level to 10,000' MSL with no problems and little discomfort.
I don't think the R-66 will be the greatest thing since sliced bread and never have, although I know a few people who do think that. Robbies are what they are, and they're not bad for flight training and inexpensive commercial ops. But I absolutely cannot wait until I get the chance to get my grubby little paws on a "real" ship like the 500.
Greatest of all time? Not even in the top ten. Attainable for mere mortals and fun to fly? You bet your certificates.