I think Freddie was bigger than the band, but he didn't want it that way. He even said in interviews that there was no leader, that they all four were equals in the band. Whether he liked it or not though, Freddie was the one thing that kept Queen in the spotlight.
Tough to say if he would have been as huge on his own. They were all in bands at some point before Queen, but as far as I know those bands were never big. I think Roger and Brian would have been session guys, maybe breaking out into something bigger. I would guess that Freddie would have made it, his talent is undeniable. I couldn't say for sure, but it would be a safe bet that Freddie would have gone on to big things without them. John Deacon probably would have been just fine never being in a band, he never really liked the spotlight anyways.