Hakeem was better. He won a championship while surrounded by role players, and followed it up the next year with another title. He had a more versatile game, better stats, dominated in their H2H matchup in the playoffs, etc.
But, Robinson was a remarkable player, too. His stats are similar, and he was the same type of elite scorer/rebounder/defender. His team won 30 out of 42 regular season matchups against Hakeem. I think he unfairly gets knocked down for needing Duncan to win. That’s true if almost everyone, though, including Jordan, Russell, Lebron, etc. Hakeem winning without a great player beside him is a rarity in NBA history, not an expectation anybody should be held to.
It isn't that he needed Duncan to win, it is that Duncan was the better player. That is why Robinson is different. He didn't get a second fiddle, he got a 1st fiddle and he became the second fiddle.
Let's also be fair when judging Robinson's championships. Jordan, Pippen and Hakeem were gobbling up all the titles during his prime. When Duncan came along, Robinson was over 32 and recovering from an injury. He wasn't the same player. He helped carry the load for Duncan's first few seasons, but really was past his prime when he took the back seat to Duncan. I don't know that Duncan would have won championships from 1990-1998 on his own either. So I think Robinson was a legit "first fiddle" guy, it's just that not every first fiddle wins the championship.
Actually, Duncan vs. Hakeem might be a more interesting argument.
My point was to Roy's point about Robinson being discredited while others had help. In that, Robinson's help was a better player. Both at the time and ultimately in career. Duncan was the best player on the 99 title team and he ended up with a better career than Robinson. Duncan was the better player and that is why Robinson having help isn't thought of the same way.
As to your other points, Robinson didn't even make the Finals until Duncan. Sure, if he had lost to the Bulls a handful of times that is different, but the Spurs didn't even make it out of the West, which by and large was pretty darn weak in the 90's. There is a reason the weakest title team, perhaps ever was the Rockets in the 94. Otis Thorpe was the 2nd best player on that team. The other 3 starters were Vernon Maxwell, Robert Horry, and Kenny Smith. I think you need to let that sink in. That team won a title. The following season the Rockets added Drexler and won again beating Robinson along the way. The Spurs meanwhile, made 1 WCF (95 when despite having home court Hakeem's Rockets took them out). They lost in the 1st round 3 times with Robinson and 2 of those teams were 55 win teams (with home court) (and I'm aware that the Rockets also had a lot of lean years in there, but they also had far higher peak success with the 2 titles and the finals loss in 86). Sean Elliott was on all those Spurs teams. He was by far the best player aside from Hakeem and Robinson, until Drexler on either squad during those 90 teams.
There really is no question. Hakeem was a superior player to Robinson. It wasn't really all that close and anyone that really followed the NBA in the 90's knew this.