If it was technically possible and Sony launched an enhanced version of the PSP Go that had a flash-memory format for store-bought games rather than UMD the PSP would have stood a chance against both the iPod and the Nintendo DS; unfortunately for Sony it wasn’t possible, and several design decisions crippled the PSP.
While I’m certain people will disagree, in my opinion the main mistake Sony made was going with UMD; and for Sony to be pushing another unwanted video format onto the market. While I have always preferred the form factor of an 8cm optical disc over a full sized disc, an optical disc is a bad choice for a portable electronics device because it is not energy efficient and efforts to increase how efficient it is tend to result in longer load times (because the disc is often stopped or run at a slower speed and latency is added as the disc is spun to read data). Beyond that, DVD discs (and most of their derivatives) are not durable so they require a case; and the case and game are large enough that it takes away from their portability.
