Depending on what you are lloking after regarding scale, proportions (realistic or good old chunky wargame standard).
My whole collection is Middle-earth themed, so I can share my preferences.
- Hobbits: Old Grenadier, Fantasy Warriors line by Mark Copplestone without any doubt. According to Tolkien they do belong to the race of Men so proportions should be the same. Available at Mirlinton. And some GW LotR are not bad either.
- Dwarves: early Red Box Games were perfec both in size and detail, but then Tre Manor decided to make them smaller. Early ones are available from Hasslefree. If you want units, former Vendel ones are quite nice, currently available from Sgt. Major (the range is called "Bloody day"). Some old Nick Lund's Fantasy Warriors are a must. Also, my last discovery, Fire and Ice Miniatures looks promising.
- Orcs: That's a personal choice, but I'd go for Thunderbolt Mountain's. Maybe some Mithril's for variety. Non-lotr from Harlequin Miniatures (currently available from Scotia Grendel) are good if you prefer a old school vibe.
- Gondor: Best thing I've seen to date is eBob dark Ages Normans slightly converted, with cloaks and winged helmets. Mithril's are not bad but different.
- Rohan: Anything viking-like with fine quality would do. I'm getting some Mierce Miniatures (Veterans of Mierce, Duguth Unit) as Helmings for example. Again Mithril is not bad. Tanatus Miniatures has the right vibe but some proportions looks strange.
- grey company: Game Zone Miniature, mounted squires form the Feudals range. They're perfect.
- Elves: I have mixed feelings about those. Thunderbolt Muntain's are too slim and realistic to look good near anything else. Some hand-picked Reaper's, Mithril's and Dark Sword's is my choice here.
That's all for the moment.