Microsoft Flightsim 2004, plus VF Terrain and Photographic Scenery is a good start for realistic VFR flight. (You can't seriously nav using the standard scenery for visual reference.)
Unfortunately the standard helicopters can't really be described as accurate, but there's a way of improving anti-torque on the R22 which improves it dramatically, and as the previous guy said, Dodosim's B206 is amazing. (They've a new improved version out in the next few weeks, with improved ETL and anti-torque characteristics.)
What's equally important though is a good control set up with rudder pedals and a separate throttle you can use as the collective. If you want to go all out and sell a kidney, you could afford the
www.simcontrol.co.uk helicopter setup, buy a projector and seriously improve the experience. (You can display just the control panel in front of you on a standard monitor, and put the window view up on the projector using a dual-video card.)
Si