Couple of points. First, Geno Smith wasn't a running QB or a dual threat. He helmed an Airraid offense at WV. Secondly, Smith, Kaep, Wilson and Manuel didn't come close to reaching the heights that Tebow did in college. Cam and RG3 came the closest in my opinion, but their big college successes were in single seasons as opposed to being over their entire college career.
There's other things I could single out. One of which would be SEC bias coupled with exposure/familiarity. Tebow was an every day, every week thing for 4 years. Baylor wasn't on the national scene really until RG3's Junior year after which he entered the draft. Cam had his one and done at Auburn. You "heard" about both of them as their names were thrown out there now and then, but no where near to the same extent. Kaep was out there playing in Nevada in the WAC. He was very much under the radar to even avid college football fans.
Another thing to note are the "intangibles", how much of an impact those have and how they rate in my opinion. Cam, RG3 and Kaep are better athletes than Tebow. That's a given. Cam takes a serious knock in my book in the intangibles. From what I can tell at a distance, he comes across as an immature, self centered guy. RG3 seems to be pretty much the opposite. I like the way he carries himself and I like his attitude. Wilson comes across the same way. Kaep ? I'm not so sure. Had some questions about him before, and his new commercials certainly don't help in that regard.
BTW, you might not know this, but I didn't like Tebow at first. He played for Florida, a team I despised (and still do unless it's Bowl time). I sat through all the hype about him when he was signed. I watched as he came in now and then during his freshman year and said WTF is all the hype about ? All he does is run for 2/3 yards.
Over the course of the 4 years, my opinion changed, somewhat grudgingly.