Erebos, God of the Dead
Being able to lock out your opponents from lifegain is a fairly nice, if not situational, effect. However, what really makes this card shine is the Greed-esque effect. Sure, it costs 2 mana instead of one, but it's indestructible Greed on a potentially 5/7! I'd say that's a pretty great card.
Pros: Indestructible Greed
Cons: Costs 2 instead of 1
Heliod, God of the Sun
Mass vigilance for 4 is pushing it cost-wise, but considering it's indestructible, I'll let that slide. The token generation is also nice, but it's a little too expensive. I'd rather see it at Kher Keep costing of 3, but since you can attack with the tokens, it's not too bad. Basically, that's all I've got to say about this card: "it's not too bad".
Pros: Mass vigilance, token gen
Cons: Token gen is costly
Nylea, God of the Hunt
Golly gee Batman! Do you mean that I can have a Primal Rage that costs twice as much with the ability to use Barkshell Blessing for 4 times as much?! Sign me up! Seriously though, this is the worst god. I don't think it's going to see much play outside of Limited/Standard and even then it's just going to be for the trample, not the +2/+2. The fact that it doesn't even give trample to itself is just another kick in the face.
Pros: Gives trample
Cons: Gives trample to everything else, secondary effect is way too overcosted
Purphoros, God of the Forge
This is Krenko, Mob Boss' new deity of choice. This is just a great card for red. The first ability is worth it alone, but the repeatable Banners Raised effect is great too and it's worth the 3 mana. Finally, red has something to be proud of!
Pros: Shocks opponents when creatures ETB, mass buff
Cons: Argument could be made that the mass buff is too expensive
Thassa, God of the Sea
If this isn't proof that WotC is purposefully trying to make blue the best colour ever, I don't know what is. First, this costs 3 whereas every other god costs 4. Second, the first ability doesn't require creatures to be good (black has that too, but it's usefulness can be dubious). Thirdly, its second effect makes it so your creatures connect 100% of the time. Finally, it's a 5/5 for 3. White and black have to pay 1 extra to get a 5-power god, but blue gets to be special? I hate R&D sometimes...
Pros: Scrying on upkeep, makes things unblockable
Cons: None because it's a blue card
Rating: It's a blue card, ergo 5/5