I agree with Raikou being BL (Aura Sphere means that he has very few remaining counters in UU) but I disagree with Froslass and Moltres.
Most of the reason Moltres is able to thrive in UU is because Rapid Spinners are many and are quite good in the metagame so there are plenty of openings to set up rocks. Indeed, UU has 7 viable spinners in the metagame (though I guess you could say Hitmonlee doesn't count since it's rarely used as a spinner which would make it 6) and only 5 spinblocking ghosts (though you could make the argument that nobody really uses Drifblim and take it down to 4). Compare this to OU - 3 Rapid Spinners (arguably 2 since Tentacruel is rarely used) and 7 spinblockers (arguably 6 since Dusknoir is rarely used). The ratios of viable spinners to viable spinblockers in both formats are:
OU - 2:6
UU - 6:4
So as you can see, rocks will be on the field a much larger percentage of the time in OU than in UU. Another disadvantage Moltres has is his low defenses and his weaknesses besides rock. Now, 90/90/85 is by no means bad but when talking about OU and not UU you start to wonder if it really is good enough. In addition to that, Moltres' water weakness means that it can get wrecked by a multitude of OU mainstays like Gyarados, Vaporeon, Suicune, Starmie, Latias, etc. the list goes on. His electric weakness is a bane too as it makes him weak to Gengar, Jolteon, Zapdos, and Rotom-A, the latter of whom is one of the most common pokemon in the format. And really, any attack that he doesn't resist can deal a lot of damage to him since he'll be losing half his health by switching in anyway.
Now you could say "Gates, blah blah Yanmega is BL blah blah more weaknesses blah blah worse stats blah blah why didn't you vote for him blah blah". The key difference between the two of them is that Yanmega has two of the best abilities in the game - Speed Boost and Tinted Lens. Speed Boost means that after 6 turns Yanmega will outspeed everything without a priority move. Tinted Lens effectively negates the opponent's resistances to his otherwise weak bug attacks. Both of these help it immensely in sweeping. Does Moltres have such an ability? No. Instead he has Pressure, a move reserved mostly for pokemon who can stall well. However, Moltres cannot stall well unless he has Wish support or something, so his ability is counter-intuitive to what he usually wants to do: sweep.
Likewise, Froslass is not quite BL material either. Yes, she's one of the best leads in UU. Yes, she can also spinblock and serve as a non-lead supporter. Yes, she's decently bulky by UU standards. But by OU standards she is not a great lead by any means. For starters, her gameplan would generally be to Taunt, set up spikes, and then Destiny Bond something to get rid of it and herself. This is reasonable but consider the outcome. Spikes is best when you have multiple layers of it on the field. Spikes can't hit as many pokemon in OU as Stealth Rock so in order to spread the same amount of damage you must compensate with several layers of it. Froslass will need 4 turns total before she can die - 1 to taunt their lead, 3 to set up spikes fully. Given most of the common OU leads, she won't be able to do this.
Azelf - Outspeeds her, 'nuff said.
Swampert - She can beat Swampert, I'll give her that much. A smart Swampert player won't sacrifice his chance to set up rocks ever just to KO a suicide lead and they'll probably switch out and try to mingdame the Froslass player into making a mistake to give them an opening.
Metagross - Meteor Mash, Bullet Punch, can live after Taunt, let's move on.
Aerodactyl - See Azelf. Also has STAB rock attacks.
Jirachi - Can trick her into Taunt or kill her outright with Iron Head.
Infernape - Fire Blast right off the bat helps. I guess you could say that Infernape doesn't have that much of an advantage though.
Roserade - One of the only OU leads Froslass beats outright. She outspeeds it and can kill it easily with Ice Beam.
Tyranitar - The best Froslass counter of anything that doesn't outspeed her imo. Sets up a sandstorm immediately to break Focus Sash and can OHKO with Crunch, Pursuit, Payback, etc. Unlike Hippowdon, TTar is not weak to Ice, giving him a slight edge there.
Ninjask - Who cares.
Gliscor - 4x Ice weakness...yeah...
So out of the top 9 OU leads (Ninjask doesn't count), 5 of them beat her outright, including 4 of the top 5 leads. On top of that, she doesn't set up a very relevant entry hazard and she takes a long time to set it up fully and is useless after that. Not the best supportive pokemon imo.
Anyway, didn't mean to derail the topic. Just saying that it's not likely Moltres and Froslass will move up to BL anytime soon.