Sonic’s levels in Unleashed are fast, challenging and frenetic in a way none of those other games ever really matched.
I’d argue that Sonic Unleashed is still, a decade later, the best example of the “boost” gameplay later popularized in Sonic Colors, Sonic Generations, and most recently, Sonic Forces. One PC port some Sonic fans have been requesting (including myself) is 2008’s Sonic Unleashed.
Valkyria Chronicles and Bayonetta were big surprises, only announced basically the same day they went up for sale. Sega has a tendency to release PC ports of their games on Steam out of the blue.