While I'd imagine that most Sonic fans' gazes have been on Sonic Mania (check out our hands on impressions here) this E3, especially looking at the difference in the line sizes between Mania and Forces, you'd be a fool to disregard Sonic Forces outright simply because there was a more "classic" Sonic title at the show. Sonic Mania is great, no doubt about that, but Sonic Forces is also setting itself up to be an especially awesome follow-up to Sonic Generations.
The biggest addition to Sonic Forces has to be the "player avatar" character. Although the editor wasn't really readily available for me to test at SEGA's booth, what the game did allow players to use were two separate pre-made avatars with their own specific abilities. The game's "Avatar Stages" play very similarly to "Modern Sonic" levels from Generations, though with more of a focus on platforming and less of a focus on speed. The Avatar does have access to a grappling hook that can be used to help shoot them through a level at a nice speed, but the majority of the level I played focused more on the unique equipment and the abilities that gathering wisps bestows on the player character. For example, gathering a "fire" wisp allowed me to continually jump in mid-air for a period of time, and one section had me continually jumping, collecting wisps to replenish myself as I continued my ascent.
Classic and Modern Sonic stages are more or less identical in gameplay to how they appeared in Generations. Classic Sonic had a very interesting Boss Battle against Eggman in one of his crazy machines, where you had to try and knock debris back at him floating in the background. Something to note is that I played through Sonic Forces on Switch in the handheld configuration, and it looked to be a crisp 720p. In fact, the game's graphics looked very similar if not identical to how the game looked on PS4 and Xbox One, and I wouldn't be surprised to learn that the only difference between this version and those was 30FPS versus a smoother 60FPS. Either way, the game played great (with only minor slowdowns, that I expect to be patched before launch). Even compared to the fantastic Sonic Mania, Sonic Forces looks like it'll be worth your time when it releases later this year.
Sonic Forces comes to Nintendo Switch, PlayStation 4, Xbox One, and PC sometime this year.
If you want to know more about this and other announcements happening at E3 then be sure to check out our E3 2017 Coverage Hub.