My vote is likely biased since I've never really spent enough time going through the neuroscience literature. Also, I think that a good part of the reason why I chose Golgi is because I know of him the most and I think his contributions were not only very important to neuroscience, but also to biology as a whole thanks to his work describing the Golgi apparatus.
Here is my rationale:
1. Golgi is the most important as stated above. Also, and this seems to be true for other fields, he happens to be the "oldest" of this group, thus giving him the benefit that his contributions have been around the longest (time has a way of increasing the impact of things)
2. Cajal. A shared second on my list (together with Loewi). I thought he was older than Golgi but he is not (had to check that one). When you have little else but a microscope and your ability to draw, his contributions are simply impressive.
2. Loewi. If you discovered acetylcholine then you just have to be among the top in neuroscience. This was a tough one since his contribution was definitely very important, but not as broad as Golgi's (outside neuroscience).
3. Sherrington. I really like him since he expanded neuroscience with his studies on the function of neurons. The fact that many of his students ended up earning their own Nobel prizes is impressive on its own right. If there was a second list for "who is one of the most well rounded scientists/mentors", Sherrington would be at the top.
4. Prusiner. I think that his discovery of prions is definitely commendable. Unlike the above scientists though this occurred only recently. His impact in the field will likely not be fully appreciated until many years from now.
Ramon y Cajal in my mind is the greatest neurocientist of them all. While Gogli was able to develop his staining technique, i think it was the meticuluos eforts of Ramon y Cajal which shed a light on the anatomy of the brain. The details that he captured with his drawings looking thrugh a microscope in those days are simply amazing. Even now I find his description of the brain and his understanding of the anatomy to surpass even the best in the field today.