Hello Mr. Subhajit!
It is very difficult to pick up any single hero of the Bengali film industry down the history because so many of them have contributed in enhancing it. May I choose one or two actors per age rather than choosing one?
Pramathesh Barua was undoubtedly the best hero in the developing days of the Bengali film industry. The name of Ahindra Choudhury (Natasurya) is also to be remembered with respect.
Bikash Ray, Asitbaran and then carried on the batton. After them, Uttamkumar, Soumitra and Biswajit were the three muskateers! Shubhendu was a good hero too but was far from these trio in stature and glamour. I deliberately leave out Kishore Kumar since he was more busy in the Bollywood.
Tapas Pal and Prasenjit were the hit duo in the post Uttam-Soumitra era.
Among the recents, Dev is not bad.