I am a performing professional classical musician who also happens to enjoy video games.
I am saddened by the attitude that many people have that by performing music such as what comes from games that the orchestras are somehow "cheapening their brand" or that it is "diluting the culture." To claim this is to completely ignore why people listen to music in the first place, and where much of "classical" music came from. This elitist attitude is what has significantly contributed to the decline in attendance numbers seen over the last few decades.
Mozart was a party animal. He was essentially a 18th century rock star, complete with the fame and lavish lifestyle that implies. As much as he was a musical genius, he was terrible at managing his personal affairs and died penniless, buried in an unmarked grave.
Beethoven, who is often called the "Father of the Modern Symphony" (thanks to his groundbreaking work in his 9 Symphonies), was also very much involved in the popular music scene of his day. His Egmont is music that was written to be performed alongside a production of a play of the same name (only the overture is performed with any regularity today, as the play itself is pretty awful). This makes it essentially 19th century movie music.
When Stravinsky's Rite of Spring was first premiered, a riot broke out among the audience. This wasn't just because of the nature of the music itself, but because that was the culture of performance at the turn of the 20th century - the audience was looking for something to get riled up over, and the music hit that emotional chord perfectly.
Modern performances are often formal affairs that remove the context of the music from its original conception. This isn't always a bad thing, as a good performance of a Mozart Symphony can be very exciting, but to try to stick to that because of some idea that it's meant to be that way is to ignore what the music actually is. Modern orchestral composers don't compose symphonies any more, they compose for movies and video games. That movie and video game music of today will be tomorrow's classical music. I've already seen performances of movie music from 50 years ago or so programmed into classical performances (not the pops concerts where such music usually resides), and such will become more and more common as time goes on.
In any case, something that increases awareness of the medium is a good thing. Today's kid that attends a video game concert performance might be tomorrow's grandmaster concert soloist, inspired by the music they heard when they were young. Even someone just making the leap from attending a video game concert to deciding to attend a classical concert isn't a very big one, but is extremely important to the long-term health and survivability of the genre.