Well... there is only really one, http://www.gamesas.com/index.php?/topic/1088291-morrowind-graphics-extender-mge/.
You can use ENB Series if you want, but MGE has now surpassed everything it can do.
If you're looking for
texture replacers read through the http://www.gamesas.com/?showtopic=956115 thread. scroll through it to find section on new Architecture/Landscape/NPC/etc etc textures.
You might also want to look at http://web.archive.org/web/20080514081136rn_1/ltm.ufrealms.net/textpacks/
The largest collection of options can be found in the PES http://planetelderscrolls.gamespy.com/View.php?view=Mods.List&category_select_id=13
Connary's textures are my personal favourites. They can be found through the megaupload link in http://www.gamesas.com/index.php?/topic/1082054-connarys-retextures-gonne/page__view__findpost__p__15763006
Other popular textures are from: Darknut, Vurt, Alaisiagae, Qarl, Plangkye, AnOldfriend.. etc etc etc. Look through PES until you find what
you think is best.