I would go with Bias and Lewis.
Regarding Reggie Lewis, I remember him as an ultra smooth offensive player, who was very good defensively too. Let's not forget, he played with the big three, so his offensive numbers could have easily been higher on a less talented team. I also think he played in an era, where the 2 guard was more difficult to defend. I would give Jaylen the slight edge defensively, but as far as offensively and basketball IQ, I think Reggie easily had the edge there.
I don't understand why some people here are trying to minimize Bias's potential impact. They seem to be trying to compare him to all time greats or MVP caliber players, and that he would have not matched their success. I guess my question is, do these same people think Tatum will be on par with these all time greats and MVP caliber players? I hope Tatum does reach those heights, but just like Bias, he has yet to get there. On another note, if Bias was not as potentially good as these distractors claim, then why did Red Auerbach take him with the second overall pick, who then lite a cigar after the pick was made, as if he just won another title?
To add one more scenario, if Len Bias actually played for the Celtics. Would Red Auerbach have been willing to trade Bird and or McHale? I believe Red was approached with the following trades towards the end of their careers.: Bird to Indiana for Chuck Person, Herb Williams, and Steve Stipanovich. McHale to Dallas for Detlef Schrempf and Sam Perkins. Obviously, that Bird trade proposal was garbage, but that would have been a great deal for McHale.