Nitro is number 1. To take over the role and push liquid to almost every final versus astralis, you can't deny his ability.
Daps is seriously #2. He's proven time and time again, that his system and structure can turn unknowns into star players ( optic and nrg ) he lacks in firepower but his brain is almost incomparable.
Stanislaw is number 3, this guy has decent fire power for an IGL, Idk much about his strats and structure, or mid round calls, but usually when he joins a team they improve within the first 6 months then plateaus out after.
Only other igls I can think of after them is vanity / FNS but they're only good for tier 2/3 teams..