Among some fans of the Three Stooges, it is almost blasphemy to say you liked Shemp…and if you dare utter a loving word about Joe Besser, someone will want to poke you in the eyes and run a saw across your scalp. To these folks, Curly was the only Third Stooge and his replacements were forever guilty of the unpardonable sin of not being Curly. But I really liked Shemp and I think one of the reasons most of the films featuring Shemp weren't as wonderful was because of their budgets and scripts…not because of which guy was appearing alongside Larry and Moe. Across the long history of the Stooges' Columbia shorts, the budgets just got leaner and leaner, and there was less spent on location shoots and stunts and a greater reliance on one-set quickies with stock footage. The whole market for short comedies was in steady decline and their films would probably have gotten worse and worse even if Curly had been in them.
I'll even risk bodily harm by saying that Joe Besser was just about the best thing that could have happened to the act. By the time he replaced Shemp, the films had very little to offer in terms of production values and new ideas, and Moe and Larry were getting kinda tired. Besser, with his infectious energy, was a nice shot of adrenalin for a dying franchise. He pretty much carried every film he was in — and given how cheap and repetitive they were, that amounted to a lot of heavy lifting. He was a very funny man, as he proved both with the Stooges and in his many appearances apart from them.
Here's a nice little profile of Joe…