It's cooler when you realize it was basically the bear of it's ecosystem.

Yes. They are my favorite animal. 

The "real" ones the size of a turkey? or the jurassic park like ones that arnt velociraptors, but use that name because it sounds cooler?

The Smilodon

Smilodon and Dodo Birds are some of the most famous examples.

Some others I like:

Neanderthals. The closest thing to us modern humans, with whom we briefly co-habitated Europe. Though we may never know for sure, it is intriguing to consider just how intelligent they were, what kind of culture they had compared to us, how we interacted with them. Recent evidence suggests we may have interbred, with non-African modern humans possibly containing 2% Neanderthal DNA in our genome.

Megalodon. A shark the size of a bus. Truly a terrifying prospect; as epic as they sound, I reckon I'd be petrified of going more than waist-deep into the ocean if these buggers still lived. The leading theories as to the cause of their extinction are the cooling of the oceans and the decline of the large cetaceans they depended on for food.

I do find it fascinating, the reasons why species become extinct, whether it be climate change, natural disasters, competition, loss of their food source, etc. Sadly, in recent times it's all too often the fault of us humans.

They should've just called the ones in JP Deinonychus cos that's what they basically are sans the feathers, but yeah, I guess Velociraptor just sounded more badass.

There are a few other ones that I forgot to add. But to give another good example of one of my favorite prehistoric animals ... meet Armadillosuchus 

That sh*t would be scary to run into out in the wilde, some of them were 400kg+ / 880lb+.

Another cool example of how diverse Crocodilians were.

The megafauna who lived until 10,000 years ago (like the mammof, sabre tooth tigre, cave bear, whoolly rhinocerous and so on), died because of humans hunt and eated them.