Complex sentence: Since the release of the original "Breakout" arcade game in 1976, there have been notable clones and updates for various platforms--sufficiently so for them to be called a genre by some.
Split into simpler sentences: Since the release of the original "Breakout" arcade game in 1976, there have been notable clones and updates for various platforms. The profusion and notability of such games has been sufficient in order for them to be called a genre by some.