Music games like Guitar Hero and Rock Band were one of last decade’s fastest-growing enterprises, but now they’re a cautionary fable. After peaking at $1.7 billion in annual revenues in 2008, the games fell by 46 percent just one year later, taking the entire interactive entertainment industry’s fortunes down with them.

It wasn’t fun and games for those directly involved, but for entrepreneurs, there are serious lessons in operations, marketing, and leadership at the crux of the genre’s misfortune that every business leader should know. Here is a summary of the most pressing takeaways of the Guitar Hero study.

Differentiate Product Offerings: First came Guitar Hero, which let you strum a plastic ax. Then Rock Band—which added bass, drum, and vocals—followed. Early sequels of each benefited from token improvements like better visual quality and adding more music. But later releases, largely indistinguishable, defaulted to minor enhancements for veteran players, such as additional multiplayer modes and group harmonies, and failed to offer most consumers tangible value. Charging $99 or more per software/hardware bundle (double the average game’s retail price), despite a growing swell of clones and uniquely positioned competitors, these attempts to annualize each franchise led to buyer confusion. Lesson learned: All major product and service upgrades must be paired with one to three major feature additions that offer measurable everyday worth that are easily communicable at a glance.

Don’t Oversaturate the Market: Buoyed by the genre’s seemingly unstoppable rise, no less than 75 music games were released between 2005 and 2010, including nearly 20 iterations of Guitar Hero alone (On Tour, Rocks the '80s, Mobile, Smash Hits, etc.). Not only did these new entrants further fragment the market (should you buy SingStar or Lips? Wii Music or Rock Revolution?) and perplex buyers, many like Green Day: Rock Band also incongruously played to small audience subsets. Shoppers began to gag at the prospect of buying still more plastic instruments and painfully expensive artist tributes. Reviewers panned many of the clones as being the overpriced equivalent of downloadable expansion packs—more easily distributed products with better margins. Lesson learned: Scarcity still commands a premium, and while serving niche markets can be profitable, production and distribution should be rightsized to match.

Be Conservative: Driven by the sale of $100 prepackaged sets, executives watched the then-novel music game category’s fortunes soar initially. But at the time, direct historical sales comparisons were limited, and the games priced way higher than rival categories. Rather than base projections on decades of possible references, including minor, less well-known launches, both used a handful of breakout successes specifically tied to plastic-instrument sales as touch points to found overly optimistic projections. When the field’s luster inevitably dulled (right as economic woes hit, ironically), the numbers didn’t add up. Lesson learned: Project conservatively and tread lightly in unknown markets lest you suddenly find yourself scrambling to downscale amidst the pressures of crushing overhead, unsold inventory, and rapidly deteriorating cash flow.