I too am of the fortunate age to have watched the majority of the greatest players in their prime, sans Oscar Robertson, Wilt Chamberlain and Bill Russell.
Everybody has their opinion on how they would rank the NBA players, and that's fine. It's purely subjective. The media went into a tizzy recently when Barkley didn't name Lebron in his top 5, but, sheesh, you have to leave someone out. No matter how you rank them, it will always be controversial. You can't have 10 players in your top 5.
Lebron is a amazing athlete. What he has done for a man his size is truly astonishing. To put it in perspective, he's almost the exact height and weight as Karl Malone. He's one of the greatest offensive players of all time.
That said, IMO, he's a notch or several notches below Jordan in terms of GOAT. First, Lebron is not just an average defender, he's a poor defender. Someone with his athletic ability should dominate on that end, and, except for the occasional flash, he treats defense as an afterthought. Second, he doesn't have that inner drive and intensity that made Jordan untouchable. In fairness, no one else does either.
Jordan combined other-worldly athleticism with ultra-competitive intensity like no other before or since, and he brought it consistently on both ends. Kobe had some of the same traits, however - and, I'm saying this as a lifelong Lakers fan - a lot of his traits seemed manufactured for lack of a better word. Kobe was a great player and had an unbelievable work ethic, but he wasn't quite the natural ultra-intense athlete that Jordan was.