Why do we celebrate "two time, three time etc champ" thing?

Everybody except a select few loses, especially at the top level. Showing you can rebuild yourself into a world champion again after taking a loss is the next most impressive thing to remaining undefeated. And as others have pointed out, you don't have to lose to be a multi-time champion to begin with. Changing weight classes, retiring and unretiring, etc.

I don't understand when I see boxers saying theyre a 5 time champ, that means they lost the belt 5 times and regained it.. thats not something to be bragging about. Am I missing something? I always wondered about that as well, unless it's different divisions. An interviewer once called Floyd a former two-time welter champ. To which Floyd responded, "I ain't a former anything, I'm THE welter champ." I liked that answer a lot.

Coming back to do it again after losing is a great thing

I understand the point you're making, but you're seeing it from a perspective of the unbeaten is everything sense. It must be hard to take a loss as a champion, then to come back and regain your belt has to be admired. Many fighters in history have lost their belt and never won it back. Plus, people need to realise, when the best fight the best, somebody has to lose (excepting occasional draws) So the more top match-ups we have in boxing, the more losses the top guys will have. What makes boxers world class is getting wins over other world class fighters, even if you're losing many to other fighters in that category as well. Not being 20-0 knocking over 20 cans.

I don't understand when I see boxers saying theyre a 5 time champ, that means they lost the belt 5 times and regained it.. thats not something to be bragging about. Am I missing something? Magic Johnson is a 5 time NBA champion. He lost in the Finals 4 times. Should he not brag about his 5 rings ... I'm confused.

Not true..Floyd never lost and is a 12 time champ