1. These discussions are always ludicrous because they don't compare apples to apples. NBA players are WAY better than they were in MJ's days. In particular, the abilities of the median player are considerably higher than they were. In MJ's day, it was common for NBA teams to give substantial minutes to big immobile oafs. I'm not sure Patrick Ewing would make it in the NBA today, and I'm sure as hell confident that the Greg Ostertags and Joe Kleines of the world would not. Teams can play way more sophisticated defenses now. Playing defense is much more taxing than it was. On the other hand, there are more passing targets these days to get assists (though Bird never had that problem).
Prime MJ, if fast forwarded in time 25 years, would not be close to the best player in the NBA. He'd be a poor man's SGA at best. That's not a commentary on MJ himself -- it's massively unfair to compare him to players who were able to train their whole lives in skills that MJ himself first popularized, not to mention that training is much, much better these days. This is a commentary on the NBA in those two eras. The league is just way better now, and it's still getting better. Just as the NBA was way more competitive in MJ's day than Wilt's or Mikan's.
2. To me, it's pretty clear that Lebron has had the best *career.* If MJ hadn't twice retired, it might be different. MJ also came into the league older than Lebron, because one-and-done and none-and-done didn't really exist. So compared to Lebron, MJ lost a couple years at the front end (depending, I think, on how you count), and a couple of years in his prime (though probably not his absolute peak). Just another reason it's apples to oranges.
Lebron has scored more points than anyone, by a considerable margin. He's ALSO 4th all-time in assists, and top 20 in rebounds, and in addition to that he was a great, great defender for most of his career. MJ was a great defender too, of course, but defense was way easier back then, and far less taxing.