I started out learning to fly helicopters in FSX with the Just Flight Schweizer 300CBi, which in real life is one of the most common used student training helicopters in the world. It was one of the first payware ones released for FSX, and my first payware helicopter. But it still looks good, and the sounds are great. It is reasonably priced now, and is a fairly good flight model. I still like to fly that one occasionally.
The Dodosim 206 is the about the closest you can get for accuracy with FSX. It will even keep track of maintenance costs, if you want it to.
I have the Cera Bell 412 as well, and find I fly that one the most. I think it has the most accurate looking virtual cockpit, to me personally. The flight dynamics are really well done, you just don't have all of the "bells and whistles" like Vortex Ring State, as the Dodosim 206 has.
I too have about every payware helicopter out there as well, all are fine especially the Nemeth Designs. Their MD500 and EC135 are my favorites and probably would be #3 and #4 respectively on the most flown list.
As to freeware, Mick Posch also has an excellent Piasecki H-21C available here:
http://www.mickposch.com/flightsim/fs_freeware.htm
Alphasim also released it's Sikorsky S-55/H-19 as freeware, which was available on AVSim.
Currently being worked on, and hopefully released "soon" is the "Helicopter Total Realism 1.0" physics library addon, which will finally give the default helicopters, including the Acceleration EH-101 the much needed attention and accuracy they deserve. This add on will also be able to allow users to create realism profiles for any helicopter they have in their virtual hangars.
