I feel bored and suddenly want to discuss which God is more powerful than others.
Lets see how many "Gods" in current WH40K universe:
1. Immortal Emperor - the symbol of mankind, arguable an semi-God.
2. Chaos Gods - Khorne, Tzeentch, Nurgle and Slaanesh.
3. C'tan - Void Dragon, Deceiver, Outsider and Night Bringer.
3. Eldar Gods/Godnesses - pretty much all die, the rest two are not worth to mention since they got crushed by Slaanesh singly.
4. Tau - no Gods??
5. Ork/Tyranid - I just treat them as animals, since one behave like animals and the other is truly animal.
Now, lets discuss which God is the strongest.
My ranking order:
Tzeentch > Khorne > Slaanesh/Nurgle (both are equal) > Emperor > C'tan/Eldar Gods/Eldar Goddness (both are equal).