Little more than half the players who bought the game on Steam have finished it and more than one in ten of them haven't even gotten to that very first puzzle in the solo campaign, according to the service's achievement-tracking stats. Only 55.7 per cent of players had earned the final achievement of the solo game. Only 89 per cent had even earned the first achievement, which can be acquired with virtually no effort after the game starts.
Those numbers drop even further when you look at the co-op achievements; 51.1 per cent of Portal 2 owners unlocked that initial co-op achievement, and only 21.7 per cent teamed-up long enough to finish all of the co-op puzzles.
Looking back at the stats, the biggest drop-off in Portal 2 progress occurs after the game's fourth achievement, which 79.6 per cent of gamers have attained. Only 73.6 per cent get the fifth one. There are eight mandatory achievements to earn after that, before the game is done.
The Portal series' numbers are wonderful compared to indie favourite World of Goo, which has been finished by a mere 18.6 per cent of the people who own it on Steam. 25.8 per cent have finished Trine. Then there's the co-op campaign. I can understand that people may be hesitant to try it; there's a certain type of experience fans equate with the game and interacting with others doesn't really fall into that category. Still, for every player that has fully completed co-op, there are two players who don't appear to have even tried it.
I don't mean to sound standoffish or judgmental of the people who want to take their time. Its just always interesting (and surprising) to see the realities of how people ingest games versus the way they are spoken of by the media and in forums.