There is another significant difference between Mace and Iron Man, Ant-man, Green Lantern, etc, though. They're all either in direct control of the technologies that give them power, or they're part of clearly trustworthy organizations that don't micromanage their members. Mace's powers come from the US military and - unlike Cap - are still directly under the control of the US military/govt., which could take them away at any point and give them to someone else, or give them to lots of other people without taking them away, etc, etc (depending on the exact nature, of course, which hasn't been fully revealed yet). Therefore he doesn't really have control over them, and could at this point still turn out to be nothing but a prototype prior to a much wider use of the serum as a weapon.
It's understandable that a situation like that could give rise to questions about the difference between 'superpowers' vs. just powerful weapons (hell, in another continuity Icers could count as a superpower, but here they're SHIELD standard issue). There does come a point where something can be so divorced from the individual that it's hard to count it as a personal superpower (ie, one 'Yellowjacket' is a supervillain, but an army of 'Yellowjackets' is just a really strong army).
Of course, Coulson was mainly just angry in the scene, not reasoning out the proper terminology for Mace's serum.
