Honestly, I dislike about 90% of D&D monsters. I'm such a fantasy snob, it's just awful. It's a real problem for me. I wish I were more open-minded. I don't have a problem with alot of the monster stats, but in a homebrewed campaign world I would find myself giving most of them a visual "facelift" and eliminating abilities I hate such as at-will teleportation.
It's really the depiction in art that blows alot of the D&D monsters for me, but that's realtively easy to overcome via one's imagination. I feel that the physical descriptions of D&D creatures lean way too heavily on science fiction influences. Their function in game-play is a different matter.
It would be easier for me to list the monsters I do like, as far as the look of them. I like dragons, because they are so universal and iconic. I don't like alot of creatures from actual real-world myths and legends from a variety of different cultures showing up in a hodge-podge setting like D&D. Alot of the separate species in D&D are just different names for the same type of creature stemming from different languages.
Many well-conceived, original fantasy creatures that appear in works of fantasy are only vaguely described in the text, or described in such a way that a visual interpretation would leave alot to an artist's imagination. An example that springs to mind is the "salamander" in Gene Wolfe's Book of the New Sun, which is really an alien creature that produces deadly heat, and which Wolfe calls a salamander because it is the closest fit for the creature, out of his habit of using historical terms for things which have no real analogue.
The point is, it's a cool monster, and it's really bizarre, but an artist's interpretation for inclusion in a D&D monster book might totally ruin it for me. I don't even like the way dragons are drawn in 3rd edition.
I hate dinosaurs in my medieval fantasy too. I don't see any problem with using the stats and describing them as vaguely reptilian predators, etc., though.
