I appreciate the sheer level of coordinative skill and quick adaptive thinking involved, and have loved boss videogames all throughout my life, but I don't honestly think it could ever hold my interest as a spectator sport in the way the 'proper' sports I've been into since childhood have done. I can imagine always coming back to footy for example as a spectacle, even if I was a true neutral (sneaky AD&D reference in there for anyone paying attention), but I don't reckon I'd ever pay to watch any esport. However, seeing the genuine highlights and amazing plays is certainly interesting and entertaining, in small doses.
Rocket League is one of the most accessible up & coming ones, I'd say - everyone, from all walks of life, can understand what's going on pretty much at all times, and most would be able to appreciate the level of smart anticipation and delicate control being displayed. It's more 'sporty' than most of them, while still being distinctly arcade-videogamey, as opposed to a sophisticated sports sim.
I think I'd be more interested in less frenetic, more cerebral skillful gameplay as a spectator. Waching FPS stuff frankly just bores me rigid, however high-tempo the action - in fact, the more frantic, the less it actually holds my attention. I'd be more into a slower-paced, more crafty & imaginative game, the drama being built up from seeing perfect stealthy execution and novel outside-the-box trickery unfold, rather than some annoying twat shouting play-by-play commentary as a way of directly telling everyone when you're supposed to be excited.
Videogames are to be played, experienced subjectively, so as a spectator sport it needs to be some real special shit you'd not normally get a chance to see in your own playing instances. I can dig watching fighting games when every single split-second move and counter is clearly utterly deliberate and calculated, honed to an instinctive fine art, rather than the mad intuitive button-mashing rush of doing it yourself against others of a similiar skill level. Any RTS or MOBA bollocks just gets old fast for me.