Depends on a game, obviously. Mobility, attack or something else are typically better than tanking, but there are some exceptions, where tanking is alright. Though these games aren't exactly the kind that this question was directed to.
In Starsector, the tankiest ships have two advantages. One is typically also having lots of weapons, so they aren't exactly slouches, but the other is the fact that shields and weapons draw energy from a common pool, so if you don't have enough armour to just tank enemy shots, you'll have to power up your shield instead of your weapons.
In World of Tanks, an otherwise really fucking shit, jewish whaling simulator, heavy tanks "tank" by outright negating damage. If the enemy can't penetrate your armour, he can't do damage, period. Obviously, there's fuckton of ways (including p2w ammunition… tankfags can't get a break) to attack from a better angle or exploit weak points, but if you're good, you can tank many times your HP without actually losing your HP.
Dawn of War II: Retribution's Last Stand mode allows some tanky builds as well, though they typically are no good if there are no damage dealers in your team.