Someone recently crunched Call of Duty 4: Modern Warfare Xbox Live achievements numbers. 

Three million players did not complete the intro tutorial. 30% of the uniques. That in my mind is most interesting statistic. What does this mean, other than the fact that 30% of the players don't care for getting even the simplest of achievements?

It possibly could mean that people were already well familiar with Call of Duty 4. They bought multiple copies of Modern Warfare and played the Xbox 360 version exclusively for the online matchmaking. Probable, though I would imagine hardcore FPS players would pick keyboard and mouse PC over Xbox 360. The other options are DS -> Xbox 360 and PS3 -> Xbox 360. The former? Maybe in a universe where Pikachu and Master Chief share the same demo... I can't imagine DS players skipping single player. The latter? Not likely. Most people would pick one "serious" gaming platform or the other. I own the PS3 and PC versions, and only play multiplayer on my PC. 

It could mean that single player was completely uncompelling in comparison to multiplayer. Now that's just a contention I can't fathom. Modern Warfare has arguably one of the best FPS single-player campaign in years. Missions are unique, non-repetitive, scripted dramatically and paced brilliantly. They could have sold the game as stand-alone single-player and it would have been a triple-A seller.

Or it could just mean this: the on-rails tutorial which teaches the basics of gameplay was too difficult for 30% of the players -- basics such as how to pick up and use weapons, how to move, and how to interact with environmentals such as ropes and ladders.

The follow-up assumptions here are: either the players stopped playing entirely at the tutorial, or they went on to multiplayer and hopefully just figured things out. Either way, very far from ideal.