That's an excellent letter Erin, good for you.
Since I like to play devil's advocate, though, let me just throw this one out there: like many of you, games are probably my number one hobby. I work part-time in the industry and I am as passionate a defender of the medium as anyone out there. However, while I may not agree with the black-and-white rhetoric of Fr. de Souza's article, the padre has a point.
My freshman year of college was very nearly sucked whole into the vortex that was Doom and text-based MUDs. Those are somewhat more sophisticated games than Tetris, but my overall experience was similar to that of Fr. de Souza. Naturally, I don't blame games for my terrible academic performance that year, I blame myself for my lack of maturity and poor impulse control. Still, the fact remains: over the years, I've lost more productivity to games than any other single factor.
As has been suggested in this thread, if not games, would it have been some other obsession? Possibly. Any hobby can take that left turn into obsession under the proper circumstances, but I think most of us would agree that gaming is more prone to that sort of derailment than most other "respectable" pastimes. I think that if we can avoid couching it in the sort of good-vs-evil loaded language that is used in the article, this could be a useful topic of discussion to have with parents who may be non-gamers.