Well, I wasn't looking for optimization as such, I was asking more for opinions and diverse responses comparing combinations of what is, to each individual, the 'best' - which could mean optimized to some (obviously, it does to Joe Liker), but to others it could mean the most flavorful or the...
I am leaning towards a bard/cleric as the best theurge multiclass. Wizard seems more obvious than bard at first glance; but the lore bard is a competent full arcane caster and blends well with the cleric.
And an eldritch knight/paladin seems the obvious gish theurge. But I could see many...