I have as many DC games as I do N64. The Dreamcast has proven quantity doesn't much matter when almost every title is a must-buy. Ok, now the positives. I can think of a system costing twice as much in which you get neither. For my money 4 controller ports is one of the most important features for a console.
Consoles are all about multiplayer.
Games like Powerstone, Virtua Tennis, Chu Chu Rocket and more make the DC one heck of a party machine. The modem hasn't been much of a big deal to me, admittedly. I used it quite a bit earlier in the year with the Chu Chu Rocket but haven't since. However, right now, it is Sega's main selling point. Seganet, Sega's online gaming network, has been a pretty big seller thus far.