I think of Serious Sam as the spiritual child of Duke Nukem. The game is about mowing down mindless hordes, while having fun and cracking jokes all the time. The story is not particularly compelling, the AI isn't great, the levels are not stellar, but yet the game is just full of fun. The models and environments are very well done, and the weapons assortment is very nice. The game is stable, yet can be very demanding of the hardware to keep up framerates.
This game is a 'budget' ttitle, which caused me to pass it over for a while. I'm glad I got it, because it is fun, well worth the money. However, it is a one-act show, and I've not felt compelled to play it a second time, or relive any special moments. In fact, I played the Second Encounter first, so I couldn't bring myself to play more than a few levels of the First Encounter before putting it down for good.