Prime Agassi? I say number 2 or 3 perhaps. Prime Agassi for me is better than Murray currently is, also a bit better than old Federer generally (Nadal has been forced down to 5 through not playing) but the only issue is consistancy. Agassi wasn't that consistant in majors even in his best years. Only 2 years (1995 and 2001) did he progress beyond the 4th round of all 4 majors. So though prime Agassi would be potentially the best player in the world, dunno if he could keep that level up enough to be number one. But he could probably get to 3 or 2 by winning a slam and some masters.
How to clarky - work out most or only realistic outcome, claim the opposite
Federer, Djokovic, Delpo fan (also like Nalbandian, Dimitrov, Tsonga)