I don't watch streams of fighting games either so I don't really know. You could watch the popular ones like SF and Tekken. It depends on whether you've played the games to appreciate it really. Some people like Blazblue but I don't really know much from the rare hours I played it for on my cousin's console. However, I do remember playing King of Fighters a lot a few years back so I guess you could look into it if you're interested. I have no idea how the new KOF looks like but it's nice to see the familiar characters and aesthetics.
Whenever I watch streams, I usually watch if the game looks interesting or for the streamer themselves. Some of them are probably the funniest people I've ever heard.