I agree with most of what Sean said, probably all, but I can't remember all the points as there were so many! I think that history and prestige definitely tip the scale favourably when ranking a course, as does championship status. I think this is wrong. I have played a lot of good heathland courses in the past four years, mainly as a panellist with golf monthly but also on work events. It was hard to get perspective at first and many of the scores I gave early on were with little knowledge of comparing similar standard courses - so the ratings, while not wrong (although I think what I mentioned above influenced my unintentionally), will change a bit if I rated them now. What I am finding is that there is more charm and interest in some of the lower ranked courses than the more premier tracks - now does that make them better? A case in point: I was really excited about playing Wentworth and I am sure that the fact that i got a few complimentary rounds, especially early on, probably influenced my rating. Now, I would rate the West course near the bottom of the Surrey/ Berks league as I think many of the other courses are better. It is here that I think difficulty/ prestige/ history tips the balance in favour of some courses when it shouldn't, as I scored Wentworth better, with hindsight, than I should have.
Similarly with championship tracks - I have never played the Belfry but from what I have heard, it is not that great - from everyone I know who has played the Belfry and my home course Bearwood Lakes, not one person who rate the Belfry as anywhere near as good. Indeed, I love playing at Bearwood, so I would vote that it should be in the list because I rate it as the best example of a parkland (with some heathland characteristics) course that I have played, and it is only going to get better as there has been no architectural changes since it was built in 1995 and, if they ever get around to it, they are going to get the architect back to suggest improvements over the next 10 years, to run alongside ecological, machinery replacement and other plans they have. I personally think that Bearwood is a much better course and more enjoyable experience than Wentworth, and I think that is another reason to for it to be nominated.
I think you get the best idea of what makes a good course by reading other people's honest unprompted views (i.e. not a pannelist) - that is why I read all the reviews on top 100 courses - it is here that I learned about interesting courses like Beau Desert, Whittington Heath, Ipswich, Sherwood Forrest, Southerndown, Bovey Castle, Broadstone, East Devon, Ashridge, Woodbridge, Thorpness, Delamere Forest, Sandiway, Seaton Carew, Berwick-upon-Tweed, Leetham Grange, Spey Valley and others that are generally outside most rankings but sound like they could be just as good as many higher ranked peers - and they are on my must play list. By reading these reviews, you also get good impressions about what highly ranked courses tend to disappoint - Wentworth West, Belfry, Troon etc.
I think someone will come away with a worse impression of a course ranked in the top 30 than if it were near the 200-rank, simply because their expectations are undershot, compared to if it were a "gem", then they may have been exceeded - but even so, would the fact that it was rated higher initially tip the balance by subconsciously making you believe that you have missed things and influence you push up your ratings? I think it impacted me more when I had played less courses - I now don't think it would, but you can never tell.