I think your LHS is probably correct that the latest Real Flight is probably the best out there. I have the older G3.5 which isn't too bad either. I believe tower Hobbies still has that one for a lot less than the 4.0.

I've tried the simulator that Horizon put out too. It's not quite as good as Real Flight in my opinion but not too bad either. Plus the price is great.

That being said, there are some really inexpensive simulators out there such as FMS. Are they as good as the more expensive simulators? No but if you look at the price, they are not bad at all for what you pay.

Whatever you get don't be fooled by how well you do on it. Many people do some really great flying on a simulator which builds a false confidence leading to a crash when they fly real airplanes. The simulator is a great learning tool and a lot of fun but it still isn't a replacement for real flying.