I haven't played Mario Kart 8 Deluxe, but I would like to see Nintendo release the additional content (especially the Battle Mode) for WiiU at some point. They won't, but I want it.
MK8 and Sonic Transformed are really close for me. I like the character roster and diversity of the tracks in Transformed more, but the karts and the actual course design in MK8 more. MK8 still suffers from horrible rubberbanding, but the higher levels of difficulty in Sonic are just unfair sometimes. Items are a wash for me, but Transformed is an improvement over the first game. As for the announcer, I liked him in the first Sonic Racing game, but turned him off completely in Transformed.
I have Sonic Transformed on Vita and WiiU, and have unlocked everything in both sans the mods that require winning on the highest difficulty. I go back and forth on getting the Steam version when it's on sale for the PC specific characters, but haven't yet.