5) Creative Leaders/Stonehenge
Creative leaders have their perks, but I was surprised to see a poll on this site which had Creative leaders the second most popular behind Philosophical. From the perspective of playing at a higher difficulty level, the benefits of Creative are pretty much limited to the early game--i.e., the time when the AI is cheating and ahead of you anyway. It is still good to have on a crowded map, but choosing Creative essentially amounts to using one of your leader traits to not fall as far behind in a certain area, as opposed to one that persists throughout the game and will lead you to victory.
One of the other most-cited reasons for not going Creative is that Stonehenge performs the border expansion for you at half the pace (and a cheap price), while guaranteeing an early Great Prophet and centering you on the map to boot. Of the three early Wonders (Stonehenge, Oracle, Pyramids), I would argue that their benefits are much more closely aligned to the cost of building them (120, 150, 450 on Normal speed respectively) at Monarch or above than on lower difficulty levels. Being able to run Representation early at Monarch (science and happiness will be your two biggest concerns after you've built a military) is far more powerful than getting a cheap tech for free, which is probably slightly more powerful than automatic ten turn border expansion (until Calendar, which you will need far earlier at higher difficulties). You also, once again, need to get on Stonehenge early to get it--you need a Worker, Bronze Working, and Mysticism, and that still might not be enough to stop Gandhi from beating you.
Overall, Stonehenge (as well as the Oracle) are probably overpowered at lower levels--you can get a religion, take your time getting to it as long as you chop, and get the benefits of one or both (as well as an early shrine) with a low risk of falling behind or getting whacked for not having spent your hammers on something better. Meanwhile, the Pyramids do not have as pronounced an effect (though the early Great Engineer is nice) and a prohibitive cost as well--why spend 450 when the 120 or 150 is a better bargain? Up against a cheating AI, however, the value of Stonehenge and the Oracle go down, while the Pyramids become much more attractive. If you plan to go for an early wonder on Monarch, which one you choose becomes a much more nuanced decision.
6) Philosophical Leaders + Parthenon
When I started playing the game, one of the first things I did was go Philosophical, rush to the Parthenon, plop down a bunch of farms, and run away from the Warlord/Noble AI with my GPs. It didn't matter that the Parthenon expired at Chemistry, because I'd already won by then. It wasn't even close.
GPs have considerable diversity if you are able to generate the kinds you want, and have a use no matter what type of victory you are going for. There are a couple things that are going to hinder your ability to produce as many GPs as you did on Noble though, the most important of which is the increased importance of production and commerce. Failing to keep a good military and/or failing to keep up in the tech race is ultimately the cause of losing any game, and choosing to emphasize food/specialists in one or more of your cities ultimately means you are not emphasizing production or commerce there (with the exception of the food bonuses, almost all tiles that are high food can also become high commerce). Engineers, Scientists, and Merchants make up some of the ground, of course, but in some (if not most) cases it will be more efficient to just make your high food city into a high commerce city.
I don't mean to imply that Philosophical civs are less powerful on higher levels--Woundedknight has already shown in his article that a Philosophical civ can excel at the higher difficulties, so it is certainly good enough to help get the job done. But getting the Parthenon is subject to the same pitfalls as the other early wonders, and it can be argued that the Pyramids (for 50 hammers more) encourage the use of specialists just as much, while giving you Representation and highly desirable Engineer points instead of Artist points. Ultimately, I think a Philosophical + Parthenon tactic is not a good one to choose if you are just getting your feet wet at Monarch--it will require a lot more skill to pull off than simply pushing for production and commerce (or the Pyramids).
7) Financial Leaders + Kremlin
There's no way I can argue that going for the Kremlin is a bad idea if you are a Financial civ, if you have high commerce like you should, and if you have the production capacity in one of your cities to beat the AI to it.
There are times when it might not be as good an idea as some other move. Like not having met all three of those conditions. Another strong reason to not go for the Kremlin at Monarch or above would be if you are in a neck-and-neck tech race (as you probably will be). Communism is a dead-end tech, and there are several of military techs to be gained at this point in the game, including most of the modern navy units, Artillery, and Infantry. It's one thing to fall behind a tech or two, and an entirely different thing to fall behind a military tech or two. Communism, of course, is needed eventually (spies), but rushing to it could mean somebody grabs Assembly Line at the same time and renders your military less-than-modern. You will be able to compensate by buying units, of course, but you are still behind in military techs and have to catch up. The Kremlin remains a powerful wonder capable of pushing your civ over the top, but only in the right situation (such as a one or two tech lead).