Got it backwards.
Jimmy Fallon can be funny but as a host, he's sooo awful.
The thing people forget, The Tonight Show is bupkis. It's should not be a Holy Grail to anyone. It was all about Carson. Had Johnny Carson not been on the air for decades, The Tonight Show would've been a forgotten program, probably canned in the 60's. Who even remember who hosted before Carson? Steven Allen? Maybe?
Any late night host is better off NOT getting the job because they will never measure up to a "legend".