Ice at #3 seems pretty clear-cut there.
Jellicent, sorry, but you haven't exactly argumented your opinion there. You just made a lot of statements (some of which I don't agree with, for example Ice being the best special offensive type in the game: no matter how awesome Blizzard is, you are not beating a lot of Pokémon with it, while Psychic can potentially beat everything, even Chansey and stuff that resists it), but you failed to
compare Ice and Ground, which should be the whole point.
I will go back to my criteria list. I don't know if you guys agree with it or not, personally I think it is more useful than comparing how good each type is offensively and defensively, because that just encourages people to look at the type chart and not at how Pokémon and attacks actually affect the metagame.
(For example, saying that Ice has no real weaknesses is a mistake. While it's true that weakness to Fire, Fighting, and Rock are almost irrelevant, this statement fails to notice that all existing Ice-types are dual types and so have real weaknesses. All Ice-types but Jynx are weak to Electric, and Jynx's Defense is so low that she might as well be considered weak to every physical attacking type. Ice is sort of on the same boat with Ghost, defensively speaking. Awesome if you just look at the chart, much more troubling if you look at the actual Pokémon. Except of course weakness to Electric isn't as huge a deal as weakness to Psychic and EQ.)
So anyway, back to the criteria list.
1. How Pokémon of that type perform in the metagame.
Ice clearly wins here. Not only are there a lot of good Ice-types, but every Ice-type Pokémon but Dewgong is viable and has a niche in the OU metagame.
I would have argued that Ground-types are still more common overall than Ice-types, but I guess I have been proven wrong there.
2. How attacks of that type are important in the metagame.
Ground wins here. I would like to invite you all to make a thought experiment.
Imagine what would happen to the OU meta if Ice Beam and Blizzard didn't exist. Clearly Exeggutor, Victreebel, and Dragonite would become much much better, Chansey could no longer rely on freezing to beat other Chansey, and Starmie would probably see much less usage, seeing as it would only invite Exeggutor to switch in. Some match-ups would be screwed up (like Exeggutor vs. any Ice-type), but the metagame would still be recognizable.
Now imagine what would happen to the OU meta if EQ didn't exist. Suddenly Tauros would just become a Persian variant and Snorlax would have to rely on Psychic to be able to scratch Gengar in any significant way. The metagame would be turned completely upside down, with special attacks being much more central than they are in the real meta.
The point I'm trying to make is that while Ice attacks are awesome, freeze chance is a bee's sneeze, and all that stuff, Ground is part of the reason we even ranked Normal #1! How do you get more influential than that?
3. How influential the typing is in the above two factors.
No one can deny that Ground is a very influential reason why GolDon and EQ are what they are. None of them would probably be used at all if they weren't Ground-typed.
What about Ice? Ice is a wonderful attacking type, so no doubt it is a very influential reason Blizzard is so common. The answer is not so clear-cut regarding the Pokémon however.
While Lapras and Cloyster both enjoy being Ice-types, this isn't the main reason they are used. If they were both pure Water-types, they would still be viable and their effectiveness wouldn't be shaken by much.
Jynx would seriously be injured if she were a pure Psychic-type, but the main reason she is used is Lovely Kiss, so I am guessing Ice wouldn't be that influential either, other than a weaker Blizzard.
Finally, Articuno completely relies on its Ice-typing to be viable, otherwise there's no reason to use it over any other Blizzard user. The thing is Articuno isn't very common to begin with.
Bottom line is, while Ice is a nice defensive typing, it doesn't give you anything that can't be obtained in other ways. Resistance to Ice attacks can be found in Water-types (the advantage of Ice-types not being weak to Electric is purely theoretical) and in generic special walls like Chansey, and the immunity to freeze, while great and unique, isn't as fundamental because freeze is unreliable.
The Ice typing is much more important offensively, both for the Pokémon that get it and for Blizzard/IB, but the thing is Ground beats Ice as an offensive type for the reasons I explained above.
