I feel like this thread is done once every few months, but he is absolutely not a first ballot HOF player.
He was/is a very good player that performed at a high level, but he was never considered the best HB, and possibly only a few times would you consider him a top five HB. First ballot is for players that were elite and unquestionably the best or top two or three at their position (depending on position) for a significant portion of their career.
He was very, very, very good during his prime, but there are probably 10+ HB's since he's been in the league that had higher peaks and primes than Gore.
Probably one of my favorite five HB's I've gotten to watch though.