^---yes that is the only "unforgivable" sin mentioned i the bible
Mark 3:28&29 - I tell you the truth, all the sins and blasphemies of men will be forgiven them. But whoever blasphemes against the Holy Spirit will never be forgiven; he is guilty of an eternal sin.

also

Luke 12:10 - And everyone who speaks a word against the Son of Man will be forgiven, but anyone who blasphemes against the Holy Spirit will not be forgiven.

...but as far as the others no sin is really considered greater than another, the only thing i could find that pointed out any other sins as worse than others was in 1st Corinthians 6:18 where it says "Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body."

but the bible also says that there are different sections of hell for different groups of people...i take this to mean that hell will be worse for people who have either sinned more often without remorse or for those who commited "heavier" sins like murder and such...i'd like to think that someone like charles manson would have it harder off in hell then i would