Thinking back on Phantasy Star Online today, a game where you'd venture out with three other people to complete missions and take on enormous boss fights, it was like a preview of the co-op experience we'd get with games like Destiny, Anthem and The Division. The Dreamcast arrived years before I had a PC that could actually play games decently, so for me, and many other gamers, it offered a formative online experience. Nowadays, the only way for me to relive that PSO high is to hop on a private server.
In comparison, online support was practically an afterthought for the PlayStation 2. Sony sold modem and broadband adapter add-ons, but few games took advantage of them. Microsoft, which worked with Sega to implement Windows CE on the Dreamcast, made broadband gaming a key feature of the original Xbox. Ethernet connectivity was built into every console, and with the launch of Xbox Live in 2002, there was finally an easy way for console gamers to play online like their PC brethren. And even without that service, the Xbox was a solid LAN gaming machine (at least, based on the many hours of Halo multiplayer I clocked in college).
While the Dreamcast was certainly prescient about the importance of online gaming, it came a bit too soon. It took a few years after its 1999 launch for broadband to become mainstream in homes, and to take advantage of that, you also had to buy a separate adapter. Who, but crazed PSO fans like myself, would do that?
It's basically the Xbox 0.5
In a broader sense, it's easy to see how Microsoft learned a few lessons from the Dreamcast. It was a console that failed due to a lack of third-party support, extreme marketing competition from Sony, and, unfortunately, bad timing. While the original Xbox repeated some of those mistakes, come the Xbox 360, it was clear Microsoft finally figured out how to wrestle with Sony.
If you squint a bit, the Xbox 360 even looks like a Dreamcast sequel, with its sleek white case and circular logo. (This 2005 1UP article lays out some truly eerie similarities, including the fact that executive Peter Moore was involved with both console's launches.) Xbox Live also evolved into a much more useful service on the Xbox 360 -- something that was integrated throughout the entire console.
Other noteworthy tidbits:
The Dreamcast's controller accessory, the VMU, predicted remote app support for games like Destiny and the Wii U's dual-screen play.
The basic layout of the Dreamcast's controller would also be replicated on Xbox systems and other pads, like Nintendo's Switch Pro Controller.
It was also the first console to user a higher-capacity optical disc than CDs, the 1.2 GB GD-ROM.
With a cable accessory, you could also get 480p output from many games. It wasn't HD, but it was the closest we could get until HDTVs went mainstream around 2005.
If you can't tell by now, the Dreamcast holds a special place in my heart. It was the first console I bought for myself, after toiling away for months as an electronics sales associate at OfficeMax. I also lucked into a pile of excellent games early on, thanks to affiliate sales from my anime fansites. Mostly though, it was the rare gadget that made me feel like I was actually seeing the future first-hand. Twenty years later, turns out I was right.