It's absolutely valid to compare age... LeBron had a 3 year head start on MJ because he was better than MJ during their 18-21 year old years. Just because MJ didn't play in the NBA and LeBron did, doesn't make it invalid. In fact, that should work in LeBron's favor.
Pippen the 2 reg season years without MJ:
93-94: 22 ppg, 8.7 rpg, 5.6 apg, 2.9 spg, 0.8 bpg. 49% FG shooter
94-95: 21.4 ppg, 8.1 rpg, 5.2 apg, 2.9 spg, 1.1 bpg. 48% FG shooter
Do you know how many seasons in NBA history a player put up: 22.0 pts, 8.0 rpg, 5.0 apg, 2.0 spg?
3 times (MJ, Larry Bird, Scottie Pippen)
http://www.basketball-reference.com/play-index/psl_finder.cgi?request=1&match=single&type=totals&per_minute_base=36&per_poss_base=100&season_start=1&season_end=-1&lg_id=NBA&age_min=0&age_max=99&is_playoffs=N&height_min=0&height_max=99&birth_country_is=Y&as_comp=gt&pos_is_g=Y&pos_is_gf=Y&pos_is_f=Y&pos_is_fg=Y&pos_is_fc=Y&pos_is_c=Y&pos_is_cf=Y&force
os_is=1&c1stat=pts_per_g&c1comp=gt&c1val=22&c2stat=trb_per_g&c2comp=gt&c2val=8&c3stat=ast_per_g&c3comp=gt&c3val=5&c4stat=stl_per_g&c4comp=gt&c4val=2.0&c6mult=1.0&order_by=player
I have no idea why Rodman isn't considered a big 3. Rebounding might be the second most important thing in basketball and Rodman was the best rebounder since Wilt? Kukoc at that point was the best European player in the NBA? Not calling him a superstar/elite player, but he was really solid.
LeBron was horrendous last night. 100%. I don't think that matters in the big picture as long as they win and if they win it all. But he was horrendous last night.
Also, MJ quit. Pursuing other interests is just a euphemism for quitting. I don't have an issue for MJ quitting, but if we're adding up everything, MJ quitting should be a negative to his basketball legacy shouldn't it?