Care to elaborate on what your top five would be? I agree that Eiffel ended up way overrated: it's really not that much tourism and doesn't benefit well from multipliers or anything. It's just +12, 5 happiness, and call it a day.
In my experience, there are only three Wonders in the game that will make-or-break it regardless of victory condition (as opposed to Sistine Chapel, which is basically essential for one victory condition, but won't help you unless you play to a fairly specific strategy): Petra, the Hanging Gardens, and the Temple of Artemis (the latter two in combination pretty much = game won unless something gets in the way, like an invasion of that city. I played an OCC culture game with all three Wonders in Palenque yesterday; my first BNW Immortal win).
In all these cases, the reason they're so critical is that they set you up for grabbing other things you need, including other Wonders whose effects are on the face of it more powerful; this is why the early Wonders are really the strongest. Petra is of course amazing, but there's no point having all those extra-productive tiles without the food to quickly grow a population that can work them quickly. I made the case in the G&K Wonder Elimination thread that the Hanging Gardens is the best Wonder in the game, and still consider that that's the case - in G&K I don't recall it coming with a built-in National Epic (i.e. maintenance-free Garden), not only earlier than you'd otherwise get a Garden but with the built-in food boost needed to populate the guilds so you can make use of it.
A lot of people think of it as just a food trade route substitute, but that's no more true than that Statue of Liberty is a factory substitute just because it provides the same resource in much the same quantity. It's additive with food trade, or depending on strategy can be used to use that trade route to earn money that can buy universities etc. earlier - and you need quite a specific, resource-intensive set-up to have two coastal cities, granaries in both, a cargo ship and a spare trade route by the time you would normally build HG (plus a National Epic, of course, to make sure the comparison factors in everything the Wonder produces). Petra can, usually quite late, get you 20+ production a turn in a city. Statue of Liberty gets you much the same much later. With a production city with as few as three mined hills, Hanging Gardens can be giving you 9 production a turn before you even hit Currency and start building Petra (how are you building it? With +9 production a turn...).
Food is the most important resource in the game, and the most flexible (food always = science, but depending on how you allocate citizens can also equal production, city growth, gold, and/or science or culture specialists); the food Wonders are indisputably the best there are, even if they don't look exciting enough to win polls like this.
For the other two of my top 5 Wonders? The two still in the poll here. I'd rank the top five along the lines:
1. Hanging Gardens
2. Petra
3. Temple of Artemis
4. Leaning Tower of Pisa
5. Sistine Chapel
Angkor Wat
Pentagon
CN Tower
Terracotta Army
Parthenon
Cristo Redentor
Red Fort
Taj Mahal
Statue of Zeus
Kremlin
Great Firewall
Great Wall
Great Mosque of Djenne
Himeji Castle
Great Lighthouse
Mausoleum of Halicarnassus
Pyramids
Brandenburg Gate
Great Library
Hagia Sophia
Sydney Opera House
Alhambra
Globe Theater
Big Ben
Borobudur
Prora
Broadway
Uffizi
Louvre
Porcelain Tower
Forbidden Palace
Hanging Gardens
Temple of Artemis
Stonehenge
Notre Dame
Colossus
Chichen Itza
Machu Picchu
Petra
Neuschwanstein
Hubble Space Telescope
Statue of Liberty
Eiffel Tower
Sistine Chapel
Leaning Tower of Pisa
Past the first few departures this is really quite a bizarre list, isn't it? I really don't get the love for Chichen Itza - I've had the experience others who downvoted it mentioned; I build it rarely, but when I do there seems to be little correlation between it and my overall success. Shame to see Great Mosque so low - it is weaker relatively speaking than it was in G&K since Borobudur does much the same thing, and with a Hagia Sophia's-worth of free faith-spreaders to boot, but in absolute terms it was better than Hagia Sophia in G&K and it's better than Hagia Sophia now, purely for the ongoing output from GM + free Mosque - certainly it shouldn't be so far behind it in the poll.
