Battles b/w pirates and marines generally end with the pirates escaping before more allies appear, so they're usually inconclusive, which doesn't make the parties involved equals. We have definite evidence to suggest Roger was ahead of everyone and their mothers and the fact that his rival remained the strongest after his death confirms it further. The most you can say for Garp is that he was not weak enough to be defeated by Roger without a hard fight.
You can't pick and choose what to accept and what not to accept. It's been said multiple times that Roger and WB are equals. So it doesn't really matter if WB had the WSM title at that time or not. It isn't mere hype, we have explicit statements confirming it for us.