1996, if BYU had lost the Utah game, BYU might not have been ranked in the years you listed.
I pointed out five additional years in which BYU could possibly have been ranked with a win over Utah.
My point is simply that the difference between BYU being ranked and BYU not being ranked (in the years BYU is good enough for such consideration) almost always comes down to the result of the Utah game.
Additionally, in 2008, the game (the 4th quarter really) was the difference between Utah going to the Sugar Bowl (with BYU to Las Vegas) and potentially BYU getting an at-large BCS bowl berth (with Utah to Las Vegas).
Edit: 2008 is the exception for BYU losing and still being ranked, albeit barely at #25 in the AP poll.