If you want the genuine answer as to why he isn't more well known or why he's not considered to be as successful, here are a few more thoughts.

1. Time. The Beatles wouldn't be as famous as they are if they sang reggae and if Charlotte Church stuck to opera she'd be not much more famous than Hayley Westenra (if you just said 'Who?' then that emphasises the point). Is classical music "the latest big thing"? No. Not at all. If Nobuo moved to France at a young age and orchestrated in the ages of Mozart, maybe he would have been as big as Mozart. Mozart probably doesn't make the Billboard 100 right now. We're in an age where classical music will not make you a superstar.

2. Sales. Exactly that. Stores won't stock what people won't buy. Gamers don't often buy the soundtracks of the games they purchase. Certainly far less often than movie-goers buy soundtracks of the movies they see, that's for sure. The soundtracks get advertised because the movie gets advertised. Let's take Cold Mountain as an example - not a massive movie by any means, but it has an orchestrated soundtrack by Gabriel Yared. It got over a million admissions in Spain alone. Final Fantasy VII sold 9.8 million worldwide (including International version). Maybe, what, one in a hundred FFVII fans got the soundtrack? I imagine by the fact that the US made well over ten times the amount that Spain did on their respective opening weekends for Cold Mountain means that Cold Mountain's already outdone FFVII and, to top that off, it's going to sell more soundtracks due to the movie-goer:soundtrack buyer ratio being better than the gamer:soundtrack buyer ratio. And there's the reasoning for that. I also read the other day that despite the increase in sales etc, the number of people actually playing video games is in decline. Crazy, but hey, if I read it it must be true

I had a three. Crap, where did it go. Oh, wait, maybe it was the ratio thing. Okay I'll just assume it is because I hate spending ages trying to remember things. Hooyay!

Oh wait it just came back to me.

3. Gamers are more likely to illegally download music than movie-goers are.