It really depends. You can't just have one dino, and say it's the best. To truly survive the ark, I reccomend
these dinos:
Ankylo
Argy
Quetzal
Spino
Trike
Meg
Icthy
Sarco
Giga
Theri
Have all of them, and you're set. However, there is one creature that trumps them all: