I think it´s great that Peterson shows respect to his other peers around the league and I am not that surprised that he mentioned Gore specifically.
Think about it: Sure, Frank struggled a bit the last seasons and Peterson may most likely be the better pure runner now, but Gore is a complete running back. He can run the ball and although Peterson may most likely be the better pure runner, Gore still is productive. But Frank also is a very good receiver out of the backfield and very good in pass protection (remember the Raiders scrimmage, where he manhandled linebackers much bigger than himself in those protection drills?) and I think Peterson knows you have to work hard to perfect those skills.
Also, Gore had to overcome a lot to make it this far in the NFL (think about his family and the devastating knee injuries he had in college), is a relentless worker in the offseason and an unquestioned leader on our team. I think other backs like Peterson can respect that as well.
Lastly, I think something else may be another underrated reason why Peterson enjoys watching Gore: When Frank has a big play, usually he runs into a whole bunch of defenders, runs over them, wiggles free and then runs into the endzone. He is no a breakaway-speed guy, but a running-over-them type. And I am pretty sure, other fellow running backs think those kind of plays are pretty exciting to watch. As a fan, I do not disagree