I don't think there is a "Best" deer rifle or best any thing else for that matter. Most of the old timers around here used the .22 short for deer hunting back during the depression. They liked the .22 short because the Game Wardens couldn't here them. Most folks changed to the 30-30 during the regular deer season but many other calibers were also used with success. My Grand father took a lot of deer with the .22 Hornet in an old Savage M23D. That rifle also kept the foxes out of the hen house and brought a few partridge home. My Uncle still hunts with a Savage 99 in .250-3000 and for the last two years, I've been using a 6mm Bench Rest.
It doesn't take much of a gun to harvest a deer. It's all about shot placement. 308 is about the biggest caliber I'd ever consider.
I think JerrScmitt summed it up right. No such thing as best. I helped my nephew buy a rifle recently and he got a Rem 700 in 30-06. He listened to my rationale even though his buddies were going big. 308 or 30-06 is the same bullit. For whitetails it just depends on range and in a pinch finding ammo. 30-06 is everywhere.