This is a slightly more difficult question than it initially seems.
I'd say regardless of start and plans, the best two wonders in these two eras are National College > Great Library. Maybe NC doesn't count because it's a national wonder, but it's so good I think it should count <_<
It starts to break down past this.
Colossus? Only available on coastal, and often useless for most of the game on Pangaea, but really really good on water-centric maps. Downside is it's on an awful position in the tech tree and on a tech that just makes no sense at all (seriously? a water-centric peaceful wonder on a tech which only benefits land warfare?). Bonus points if you're Venice since it's 2 trade routes. Stupid points if you're Venice since you just rushed iron working as Venice.
Petra? Not even available with most starts, and to some desert layouts it's not very good anyway (flat deserts it's nearly trash except for the bonus trade route - plains tiles are meh and you just built a wonder that gave you a bunch of plains tiles), but with the right desert (lots of river desert hills and maybe desert hill luxuries) it's easily better than even Great Library. Bonus points if you're Venice since it's 2 trade routes.
Stonehenge? Guarantees you a religion in nearly every circumstance... but depending on your plan (it's only useful if you care about getting a religion) and your surroundings (desert folklore/tears of the gods/goddess of festivals/stone circles/religious idols) it can be a waste of your time.
Hanging Gardens? Tradition only, but if you're going tall it's pretty good (and even better if you're going cultural). Deity AI will beat you to it every single time, so I haven't been able to play with it.
Temple of Artemis? I guess it's technically good. I dunno, it's never amazed me and I feel like it's a waste a lot of the time.
Great Lighthouse.. it's pretty nice on water maps, and it gives you a 75 hammer building you were gonna build anyway for free, cutting net hammer cost down to 110. But if you're going naval domination, which is the only reason to build it, why build Great Lighthouse when you can just wait for someone else to inevitably build it then go kill them and take their stuff? Especially when naval domination requires a lot of tech to get up and running! Barring Byzantium, you don't even get your first ranged ship until T120+ unless you skip education (WTH) or have a really fast education time (which you won't because you rushed Great Lighthouse).
Statue of Zeus: mediocre. You're a warmonger if you want this, so find the dude who built it and go take his stuff. Easy enough.
Great Wall is not so great. It can be handy if you have mostly or only open terrain around you and you're surrounded by warmongers, but you're better off making more units with your hammers instead of building the Great Wall. Additionally marginalizing Great Wall is the fact that Construction is required for it.. which means you have Composites.. which means it's completely unnecessary. (If horse units are the problem, you should've teched Bronze Working instead of Engineering)
Parthenon, I dunno. I haven't really thought about it nor built it, since Deity AI always gets it before you unless you do something stupid like skip the National College. It's not worthless, I guess, but why waste your time?
Pyramids are incredibly efficient in terms of hammers because the 2 workers normally cost 140, leaving it at a net 45 cost. The passive ability does neat things when stacked with Citizenship, like making repairs take only 1 turn. Only applicable to liberty starts, though.
Oracle is pretty nice, but I rarely build it. It comes at an awkward time because it's on the same tech as National College. It's definitely one of the better wonders in the list, though!
edit:
Two of those very much not Ancient/Classical like the thread title asks.
I'd say regardless of start and plans, the best two wonders in these two eras are National College > Great Library. Maybe NC doesn't count because it's a national wonder, but it's so good I think it should count <_<
It starts to break down past this.
Colossus? Only available on coastal, and often useless for most of the game on Pangaea, but really really good on water-centric maps. Downside is it's on an awful position in the tech tree and on a tech that just makes no sense at all (seriously? a water-centric peaceful wonder on a tech which only benefits land warfare?). Bonus points if you're Venice since it's 2 trade routes. Stupid points if you're Venice since you just rushed iron working as Venice.
Petra? Not even available with most starts, and to some desert layouts it's not very good anyway (flat deserts it's nearly trash except for the bonus trade route - plains tiles are meh and you just built a wonder that gave you a bunch of plains tiles), but with the right desert (lots of river desert hills and maybe desert hill luxuries) it's easily better than even Great Library. Bonus points if you're Venice since it's 2 trade routes.
Stonehenge? Guarantees you a religion in nearly every circumstance... but depending on your plan (it's only useful if you care about getting a religion) and your surroundings (desert folklore/tears of the gods/goddess of festivals/stone circles/religious idols) it can be a waste of your time.
Hanging Gardens? Tradition only, but if you're going tall it's pretty good (and even better if you're going cultural). Deity AI will beat you to it every single time, so I haven't been able to play with it.
Temple of Artemis? I guess it's technically good. I dunno, it's never amazed me and I feel like it's a waste a lot of the time.
Great Lighthouse.. it's pretty nice on water maps, and it gives you a 75 hammer building you were gonna build anyway for free, cutting net hammer cost down to 110. But if you're going naval domination, which is the only reason to build it, why build Great Lighthouse when you can just wait for someone else to inevitably build it then go kill them and take their stuff? Especially when naval domination requires a lot of tech to get up and running! Barring Byzantium, you don't even get your first ranged ship until T120+ unless you skip education (WTH) or have a really fast education time (which you won't because you rushed Great Lighthouse).
Statue of Zeus: mediocre. You're a warmonger if you want this, so find the dude who built it and go take his stuff. Easy enough.
Great Wall is not so great. It can be handy if you have mostly or only open terrain around you and you're surrounded by warmongers, but you're better off making more units with your hammers instead of building the Great Wall. Additionally marginalizing Great Wall is the fact that Construction is required for it.. which means you have Composites.. which means it's completely unnecessary. (If horse units are the problem, you should've teched Bronze Working instead of Engineering)
Parthenon, I dunno. I haven't really thought about it nor built it, since Deity AI always gets it before you unless you do something stupid like skip the National College. It's not worthless, I guess, but why waste your time?
Pyramids are incredibly efficient in terms of hammers because the 2 workers normally cost 140, leaving it at a net 45 cost. The passive ability does neat things when stacked with Citizenship, like making repairs take only 1 turn. Only applicable to liberty starts, though.
Oracle is pretty nice, but I rarely build it. It comes at an awkward time because it's on the same tech as National College. It's definitely one of the better wonders in the list, though!
edit:
Two of those very much not Ancient/Classical like the thread title asks.
. 
![[GandK]](/images/icons/gandk.gif "Gods and Kings [GandK]"){kind=icon}
)
... that's it, right? Desert Folklore would get you that.
