ISFDB Top 100 Lists

Note that this version of the list hasn't been updated since 2005. Current data is available here

Without question, there must be a genetic disorder in humans which compels them to create Top 100 Lists.

The philosophy of the following lists is pretty simple: all novels and works of short fiction which have been nominated for an award are scored based on the number of award wins and nominations. The results are then sorted. This is not an attempt to list the best works in the genre, just those which won the most awards. Since the proliferation of genre-related awards is a fairly recent phenomenon, these lists tend to favor more recent works. There are 3 different algorithms used in each category:

The Balanced List simply assigns scores from the various awards; this list is the most objective of the three.
The Critical List puts extra emphasis on those awards which are decided by jury. It attempts to construct a list which might appeal to those who prefer "Literate SF". It also attempts to balance the age factor by more heavily weighing older works.
The Popular List puts extra emphasis on those awards which are decided by popular vote. It attempts to construct a list which might appeal to a younger audience. It assigns an additional penalty to older works for being "dated".

The author lists use the same algorithms as the novels and short fiction, except that the scores are accumulated. Additionally, collaborations are treated as a single author since the collaborative style usually differs from that of the individual authors. The Anthologies/Collections/Magazines lists also use the same algorithms, except that the scores are accumulated per publication.

Top 100 Novels (Balanced List).
Top 100 Novels (Critical List).
Top 100 Novels (Popular List).
Top Novels (By Year). This is the list of novels which scored at least 50 points using the Balanced Algorithm, sorted and listed by year. (Note: due to the various award eligibility rules, a novel may be nominated well after it was published, or have nominations that span multiple years. For simplicity, all award points for a given work are collated into the year that the book was published.)
Top 100 Short Stories (Balanced List).
Top 100 Short Stories (Critical List).
Top 100 Short Stories (Popular List).
Top Short Stories (By Year). This is the list of short fiction which scored at least 50 points using the Balanced Algorithm, sorted and listed by year.
Top 100 Anthologies/Collections/Magazines (Balanced List).
Top 100 Anthologies/Collections/Magazines (Critical List).
Top 100 Anthologies/Collections/Magazines (Popular List).
Top 100 Authors (Balanced List).
Top 100 Authors (Critical List).
Top 100 Authors (Popular List).

And don't forget Tristrom Cooke's original Internet Top 100.

The Scoring Algorithm

Titles in the appropriate award categories are first assigned a score based upon each award nomination it received. A first place finish receives 50 points; a 2nd place (or a non-winning nomination) gets 35 points; titles which finished in 3rd place or higher get (33-poll position) points, with a minimum of 1 score of 1 point.
For Critical Lists, the score from each award determined by jury is multiplied by 5. Additionally, the score is increased by the age (in years) of the work.
For Popular Lists, the score from each award determined by popular vote is multiplied by 5. Additionally, the score is decreased by the age (in years) of the work.