It's not considered cheating for the Language Benchmarks Game, seeing as it's just a game, but it would probably be considered cheating for a benchmark attempting to compare performance for "realistic" programs.
http://benchmarksgame.alioth.debian.org/sometimes-people-jus...
>>"realistic" programs<<
For example?
"The performance of a benchmark, even if it is derived from a real program, may not help to predict the performance of similar programs that have different hot spots."
http://benchmarksgame.alioth.debian.org/dont-jump-to-conclus...