I checked Sherdog's rankings at the time that Bisping fought the guys you mentioned, and only one of them was ranked in the top 10 - Brian Stann, who was ranked at #10. Leites had previously been ranked #10, but dropped out of the top 10 right before he fought Bisping. Point being, even if we're being generous, Bisping has 2 wins over the #10 ranked MW. While those are solid wins, his resume certainly doesn't justify his being ranked in the top 10 for the better part of 6 years.
I'm not a Bisping hater, but facts are facts. He's a good fighter, but his perennial top 10 ranking is a byproduct of the UFC hype machine.