1up has published an exaltation of the iMUSE system, particular its pioneering use in Monkey Island 2: LeChuck's Revenge. And it's hard to discount the truth the writer arrives at with this statement:
Needless to say, it's hard to think of any games outside the LucasArts oeuvre where the music is just so important and organic in the overall product.
You probably don't need any education about iMUSE, but read the article anyway.
Source: 1up
But, as for games outside of LucasArts of similar quality, Wallace & Gromit's Grand Adventures used Telltale's iMUSE-like sound engine (developed by Andrew Langley) to a great extent. In my opinion, it did manage to enhance the gaming experience by manipulating the soundtrack to match the action on the screen just as artistically and as seamlessly as the LucasArts games did. :)