Is Ike Williams a top 5 lightweight of all time?

Depends on a lot of things:

How much emphasis is being placed on dominance, resume, longevity, character, h2h ability, achievements in other weight classes?

What we can pretty definitively say is that he is top 5 as far as resume AT lightweight goes.

Once you bring in guys that achieved things in other weight classes, were very dominant fighters and had great h2h ability (e.g. Ross, Armstrong, Whitaker, McFarland) the waters get muddier.