How many letters does the top answer for “video game by harmonix music systems” have?

The most common answer is guitarhero (10 letters).

Crossword clue: video game by harmonix music systems

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

guitarhero 10 letters wd-fact-v3

video game by intelligent systems 50% similar → papermario, superpapermario

video game by origin systems 50% similar → ultimaonline