Yes they are! Reilly is my 3rd Boxer and all 3 have had completely different personalities, but all 3 were wonderful animals.
We had one when I was a kid. I remember that he was a happy, happy dog who NEVER got tired of playing -- which was good cuz there were 3 of us kids, with another one on the way. My folks told me he ran away from home. Now that I'm "grown up" I'm guessing he got out (he liked to climb the fence) and got run over. I'd seen him come back over the fence (he knew where the food bowl was) enough times I doubt he ran off.
I adopted one from a member here a long time ago. He was one of the sweetest dogs I've ever had. He and I were playing fetch in the front yard one night and he fell over dead -- heart attack. Broke my heart. He wasn't that old but boxers have bad hearts like GSDs have bad hips. **** happens.