First:

I don't believe any of them are exactly equal in strength. So I think each one will lie on a different level, even if the strength difference is minute (e.g. Nynaeve and Semirhage). Even if they are on the same level of the 21 level list, RJ will still have listed them in order of strength, with significant variation within each of the 21 levels - just like Nynaeve and Semirhage, who for all intents and purposes appear to be on the same level of the 21 level ladder, although Nynaeve is slightly stronger.

So here's my list:

Demandred
Ishamael
Sammael
Aginor
Rahvin
Balthamel
Be'lal
Asmodean

My old theory remains that the two traditionally "strongest" male Forsaken were merely recorded as such due to their prominent roles in the Shadow's campaign.

Ishamael for being the philosophical and spiritual leader of the movement, and Aginor for being the father of the Shadowspawn. Neither of which requires them to channel the largest volume of the One Power.

I don't believe ANYONE matched Lews Therin's raw strength. I think Ishamael was only assumed to equal him because of the symbolic role he fulfilled on the side of the Shadow.

I think that Ishamael was a top level channeler, as was Aginor, but that they both fell short of Lews Therin's strength. I think that before Demandred and Sammael switched sides, Ishamael and Aginor were the two strongest male Forsaken.

But I think that Demandred came closest in all the world to matching Lews Therin. And that once he joined the Shadow the Shadow now counted the second strongest man in the world among its ranks.

In short, Demandred is the strongest male Forsaken, with Ishamael, Sammael and Aginor closely behind him. Now let's see the real list. Hopefully Sanderson posts it soon.