#1 Who Doesn't - The Rock

The Rock is heavily rumored to be at and possibly even win the Royal Rumble. But that is not what is the best for business. He has been a a champion before and a very good one, but WWE should not make the same mistake as it did with Brock Lesnar by making a part-timer contend for the championship.
The Rock doesn't need the Royal Rumble win to return to WWE in any case. So it will be good to see someone else winning the Rumble.
#2 Who Deserves - Rusev

There is no superstar who is a crowd favorite more than Rusev at the present moment. His Rusev Day gimmick, along with Aiden English, was the talk of the town. But unfortunately, WWE didn't capitalize on this popularity by not pushing Rusev to the main event scene.
Now Aiden turned on Rusev by attacking him, setting up a feud between the two. Rusev can be the hottest babyface if booked properly, and his journey can culminate with him winning the Royal Rumble.