Okay, since permaximum declares the discussion over (and us simple players aren't familiar with the Diablo lore) I guess this thread can be closed now.
I think they mainly just said that in D1 because then the game was all about Diablo. Not to mention Lazarus was obsessed with Diablo. Of course he's going to say his master is the strongest.
The books weren't even around then. So things might have changed since then.
I'd figure Baal would be the strongest with a title like Lord of Destruction and being the D2 final boss and all.
GLORY AND APPROBATION TO DIABLO - LORD OF TERROR AND LEADER OF THE THREE. MY LORD SPOKE TO ME OF HIS TWO BROTHERS, MEPHISTO AND BALL, WHO WERE BANISHED TO THIS WORLD LONG AGO. MY LORD WISHES TO BIDE HIS TIME AND HARNESS HIS AWESOME POWER SO THAT HE MAY FREE HIS CAPTIVE BROTHERS FROM THEIR TOMBS BENEATH THE SANDS OF THE EAST. ONCE MY LORD RELEASES HIS BROTHERS, THE SIN WAR WILL ONCE AGAIN KNOW THE FURY OF THE THREE.
The books weren't even around then. So things might have changed since then.
I'd figure Baal would be the strongest with a title like Lord of Destruction and being the D2 final boss and all.
<shrugs>
This is what it says:
Excuse the typos I took it from some site.
Doesn't necessarily mean he's the strongest or weakest.
So no I don't think the discussion is entirely over.