One more vote for rats for all the reasons of the other mammals plus they breed fast enough to create a race of mutants that may flourish in the mess we will have left...
It'll be another primate, looks like Planet of the Apes was right!
Cockroaches will finally get their crunchy wiggly chance!
Pigs.. they are very clever, and smell like guys, too.
Bears, large and omnivorous and with intelligence to match
Whales/dolphins will rule the seas (and the earth)
Crabs will form a beach based society (cf Science of Discworld)
The big reptiles will get another go, Jurassic Park was great, I want it for real
Plants finally get their go. Era of the Triffids beckons.
No-one, this was our planets one chance at organised creative societies
Other - please post