Why can't I compare Luck and Tannehill? Both are top 10 picks, rookies in 2012, and haven't proven anything at the pro level. Ryan Leaf was supposed to be the next best thing and he bombed. Alex Smith went #1 in 2005 and has been average in the pros, while Aaron Rodgers went #24 in 2005 and is arguably the best quarterback in the league. There is no way that you can sit there and tell me without a even a little doubt that Luck will definitely be better than Tannehill. Obviously Luck is the more polished quarterback coming out of college and there is a reason he went #1. Doesn't mean he is going to be a Hall Of Fame QB in the NFL.
Again, one year is not enough to determine if a QB is going to be great or a bust. To use Matthew Stafford as an example again. Sucked his rookie season. Didn't do much in his second year. Stud in year three. Tannehill likely isn't going to start a lot of games if any in 2012, so no way to determine 100% if he has it or not.
As for Barkley being the next big thing, who knows for sure? He was a stud in college? So was JaMarcus Russell. Mark Sanchez and Matt Leinart certainly don't give USC a good recent track history for first round picks.
Tannehill is the Dolphins quarterback that they will try to build around at least for the next three seasons. Want a QB in the first round in 2013 or even 2014? Forget it. Not happening.