I have. What's interesting is how even still their philosophies were/are used and praised. Especially later on, of course. But they're still looked upon as wacky, crazy, dangerous, etc. And even more interesting that the average person who really thinks these philosophers are looney, if they know of them at all, still adhere to much of their philosophies in their daily lives, beliefs, morals and ethics.

They also don't seem to know many of their cultures and governments ideologies are derived from the work of said philosophers. I find it funny when someone says they hate philosophy but follow the morals and ethics of philosophers.

All the philosophers you refer to were re-discovered after their time, or else you wouldn't be studying them. Same is often true for artists and authors. Moby Dick, a novel some consider the greatest American novel, was written in 1851, was published to mixed reviews, was a commercial failure, and was out of print at the time of the author's death in 1891. Its reputation as a "Great American Novel" was not established until after the 1919 centennial of Melville's birth. Actually, there is no telling how many future re-discoveries we have yet to look forward to.

We philosophise at times of big cultural change. Thus, you see the big philosophers emerge at the same time. Just like at the industrial revolution in Europe. That and how much the people of thier times value thoughts and philosophy like the difference between the Greek and Romans.

Philosophy like any other subject, takes place within the great conversation of its time. Philosophers can be innovative in their search for understanding, but it is easy to exagerate the extent of their originality and read back into their words an expanse of thinking that would have been foreign to them. For any idea to take hold, society has to be first primed to receive it, so too do philosophers.

You are quite right, in with the benefit of hind sight we can see clearly what some were struggling to speak of without the tools of language and scientific discovery now commonplace.

Friedrich Nietzsche for instance insisted on the idea that there were two fundamentally different forms of people, the Ubermensch and the herd, the one naturally tribal and conformist the other innovative and individual.
Over a century later it was discovered that Neanderthal man was very much a none tribal species who developed art and weapons, made wheels and discoveries long before their Cro Magnon tribal cousins who nonetheless interbred with them resulting in individuals who show high Neanderthal/Ubermensch physical and mental traits and who tend to be societies innovators, scientists, leaders and artists.

Spinoza, Epicures, Kant laid the foundations of the arguements for modern atheism and scientific thought, Plato unknowingly created the forms of thought later corrupted in to theology and Aristotle all but invented propaganda by media manipulation.

Firstly, I don't know which philosophers you studied, so in a strict sense your question remains unanswerable.
As to whether you observation might be generally true I would consider this:

1. If a work is not relevant and important in its contemporary setting it is unlikely to be generally known or preserved. so I would venture that most philosophers we know of are of their time, whatever happens to their subsequent reputation. Would we even know about Kant or Hume if they had not been published and discussed in their own lifetimes?
2. Any work that is considered relevant today must either have been written recently or historically, and therefore can only be ahead of its time or up-to-date by definition.
3. Any philosopher who is not considered relevant today but who may have been once is unlikely to come to your attention (eg Boethius) - unless he is suddenly rediscovered and becomes thereby "ahead of his time". For instance, Hegel may have been considered ahead of his time in the decades after his death as dialectical materialism was picked up by Marx and incorporated into communist thinking. Now, all that is out of fashion and so he is hardly studied at all. At a future time people may find some aspect of his thinking that can be applied to the social arrangements then prevailing; he then becomes relevant again and "ahead of his time". There's probably a name for this logical fallacy which I hope somebody here might provide me with.

Maybe because what they say is considered obvious in their time so that they are not remembered. We remember those who had insights others of their time could not accept. Socrates was clearly a shining example of this.