I've always pronounced it Grade-e-ous. But then again, I also said Rye-u and Gay-den as well.
But, not only that, but thanks to lots of Destiny of an Emperor and Romance of the Three Kingdoms I also mispronounced:
Liu Bei - Lie-u Bee-I
Cao Cao - K-O K-O
Zhang Fei - Zang Fee-I
Zhuge Liang - Zoo-gee Lang
Zhao Yun - Zay-o Un
Ma Chao - Ma Chay-O
And a whole slew of others, but those stand out the best. It wasn't until voice acting in either Dynasty Warriors or Kessen started that me and my cousins realized we were wrong the whole time.