The Dreamcast attempted to bring proper online multiplayer gaming, to the mass market. Like console onlone gaming is today. But it was an idea ahead of its time, but not my much (broadband wasn't a thing!). I played many hours online, on Dreamcast, playing Quake 3 and Unreal Tournament, and yeah, at that time, my parents kicked my butt over the phone bill!! There was noticeable lag, but I tell you, the games were still very playable.
The VMUs were great, still are now I have one again! MINI GAMES!! I know the flaws of them, specifically battery life. Today I've done, not much, other than collect the right animals for my Chao in Sonic Adventure!! Nostalgia-mania!!
Obviously, I'm biased towards Dreamcast. It's the only console that I remember fondly. Linking 2 VMUs with a friend, to trade or play mini games, then plug them in back home to reap the benefits in DC game, I did that and it was great.
Make up your own mind, of course. This is all entirely subjective. What console sparks good memories for you? Dreamcast emulation seems to be going strong AFAIK. I have Demul on PC, and it works very well. I can even transfer VMU mini games to an Android phone and play them via an emulator.