If we're talking pure talent I don't think Rice even makes the top 25 of best receivers. He wasn't especially fast, didn't have the ankle breaking jukes, and wasn't out there making circus catches. His peerless work ethic is what made him the greatest receiver of all time, although obviously spending most of his career with Montana or Young as his QB certainly helps. His ability to get open came partially from being one of those crazy 'giving 110% all game long' bastards and having such incredible conditioning that even a Spartan would be jealous, but he also exploded off the line like a racehorse and ran his routes so consistently that you couldnt get a read until he made his move.
Imagine if someone like OBJ had that kind of work ethic instead of being a 70 iq diva, he'd be literally unstoppable. The only person in the modern NFL who puts me in mind of Rice is Julio Jones, who has been surrounded by mediocrity his entire career instead of by hall of famers.