It is not fanboyism but rather canonical facts.
Grievous beat Maul fair and square with one kick.
And Maul was beating Aayla Secura while Mace was distracting him so imagine what would happen if Maul got Mace alone.
Maul is also faster than Mace now after SOD upgraded his dark side knowledge, he teleports away from Mace faster than he can react to.
And Sheev beat Maul in a duel before this upgrade, so now they could be close for each other.
Therefore Grievous > Maul = Sheev > Windu
Grievous is not a coward. He just know when it's the time of tactical retreat...
And he is also a cheater.... But that's thank to TWC 2008 in the original EU he had ball to accord warrior death to his victim.. That's why he fight Kenobi personaly because he see than Kenobi is strong so he deserve it.
Misscalculation of the scenarist.... Girevous is able to take down 6 Jedi in teh same time... A Jedi = 100 gugans.. WIth the out numbered factor it make 6x100/3=200 gugan....