I enjoyed all the Gears bosses. When I first faced the Corpser of Gears 1 I paused it and sat shocked took forever to do first time round then after that it didn't take long. General RAAM my fav boss fight of all Gears, dodging the Kyrll making sure he don't get close and quickly using Torque Bow and Sniper to take him down was fun in the end I did it with someone online.
I don't remember much bout the bosses from Gears 2 apart from the giant fish, and that boss was counter intuitive I would always run away when it went to bite the boat but almost cried when I had to go in its mouth that boss was the most edgy boss I fought on Gears oh and I loved the ride around on the Brumak XD
Gears 3 the Brumak so many time I was down and my team would revive me because they are pinned down, soo much ammo wasted but was fun, I was scared during it. Lambent Beserker I didn't want to fight this one it terrified me, to the point of sweating and taking various breaks and almost throwing my brand new controller, when it was over I was relieved and glad and Queen Mryyah I didn't find her hard at all, just time and ammo consuming I didn't die during this boss fight , I just wished there was more like chase her around on a reaver or something.
The story around the characters made you scared for them when facing the bosses because you didn't want any harm done to them and when fighting Queen Mryyah to me you feel Marcus's anger etc and the will to take her down. And then after you faced her after hearing her story I felt sorry for the Locusts