I have played games from all the franchises right from the first game of R6 that was a PC game, to SC:PT. While Ubisoft did the SC series and attempted to redo the R6 series, RSE was the original devs of GR. Now the franchises are being shipped out to 3rd party developers for some parts of the games. RSE is doing the MP part of GR3 for PC and XBox while a different dev is doing the SP part at least for the PC.
Ubi really messed up with R6:3 and while some people liked the "new" way the game played, many old school people didn't. RSE is now doing much of the work on R6: Lockdown. Ubi's meddleing with the formula of GR2 also is the reason why GR2 for PC was cancelled (see my New Coke anology posted by Prozac on the GR3 for PC forum) and different versions by different devs for the latest iteration (maybe Ubi should consider expanding the RSE development department so they do not have to farm parts of the games out to keep all development in house and led by those who know the games the best.
This poll is a hard one to vote for as all 3 games are good for their targeted audiences.
before Raven Shield and the other messy excuses of games that came under the r6 name afterwards i would have said rainbow 6 but raven shield really ruined it, i hated the unreal engine and the feel of it.
so id say GR but i didnt like GR2 much and its questionable if GR3 will improve, i hope it will.
so at the moment id say none. although GR1 is the last game i liked from ubi, and before that, rouge spear.