I couldn't think of a clever title for this matchup

General Greivous and Count Dooku versus Mandalore (Canderous), Jango, and Boba Fett(NJO)

Both the saber combatants more specialize in dueling, so I'm not sure. Canderous gets a heavy rifle and his Mandalore armor. Setting: large Kamino platforms.

Boba and Jango together would take out GG and I think Canderous could stop Dooku for long enough to get enough assistance to defeat Dooku.

Canderous is a known Jedi killer, but do you really think that he would be able to last long enough against Dooku? (I think he can, but there seem to be a lot of Dooku fans out there that would be eager to disagree)

Yeah, he could. He helped against Nihilus and survived against every opponent he helped Revan against.

Canderous was according to him the second greatest Mandelorian out there.. According to the Jedi and the Republic soldiers the Mandelorians were Jedi Killers. He could perhaps last against a Jedi as powerful as Dooku with the same lightsaber skills but I don't think he coud last against Dooku.

Perhaps in a sword vs lightsaber fight, but would Dooku limit himself that much? He follows the Dark Side and unlike the Jedi he can use the force to kill. He would be foolish if he would not do it. And if Dooku saw something that could posibly hurt him I am sure he would use every edge he can. He'd choke Canderous to death, before he would allow himself to get attacked by three people.

Second greatest Mandalorian? Who was the greatest?

Mandalore... Well okay perhaps he was the greatest in Kotor II i'm not sure... he never compares himself with Mandalore from before Kotor times anymore.