I used Gamekings for awhile, then had some unhappy experiences with boattails in general (and I had some issues with one box in particular. I've also had bad results with Interlocks in boattail. I switched to ProHunters, and have had pretty good results.
I like Sierras, I've taken their plant tour a time or three (Hornady's plant tour, too), and they make good bullets. I only hunt deer, though, and won't make any claims about how great they work on elk, moose, bison, or Cape Buffalo. They shoot great, and whitetails are easy to kill.