Comparing the Dreamcast's 200+ games with the PlayStation 2's 14,000+ games is retarded and awkward. Of course even though half of the games Fluffy mentioned sucked there are more good games on it, many Dreamcast games were ported to it too, so it is not really fair at all.
It is easy to argue that based on the releases available, the Dreamcast has a higher percentage of those games worth playing, but I think anyone in the world rather have the option to play 12x more games regardless of their quality.
If you are going to say the PlayStation 3 is the best thing to play games on based on that though... lol. Using that mentality the best has and always will be the PC as you can play literally almost every game ever created on it now, if not now then in a couple of years.
Something I want to bring to the table though is that the Dreamcast was also sort of the start of making simpler gameplay controls and options available, something almost every "Hardcore Gamer" complains to death about now. If you compare many of the most complicated games on it to the most complicated games on the PlayStation, Nintendo 64 and Saturn you will see that those might not have been deeper, but they were much harder to wrap their head around than most Dreamcast games. Something like Armored Core compared to Fur Fighters is a good example.