Are you anxiously awaiting the reviews scores for the PS3 and Wii launch games? Be anxious no longer -- Next Gen has kindly projected those scores weeks in advance by studying review scores for past console launches.
While every console launch is different and past performance doesn't necessarily predict future success, it's interesting to see how the earliest games for earlier systems have fared. Unsurprisingly, a 36% plurality of launch titles tend to be mired in the mediocrity of 70 to 80% average scores, while only one in ten games break past that magical 90% average. More surprising is that Nintendo launches (N64 and GameCube) tend to fare slightly better on average than Sony launches (PS1, PS2). In fact, the GameCube had the most well-rounded launch in the modern era, with an 80.2% combined GameRankings average.
Curmudgeon Gamer has a more detailed breakdown and downloadable spreadsheets to play with the numbers yourself.