The S.H. Monsterarts are no doubt the absolute best quality figures money can buy, but they are sadly overly expensive in western markets. The NECA figures have quality comparable to S.H. Monsterarts and cost only a fraction of the price. Revoltech figures are generally a bit smaller than S.H. Monsterarts figures, but are just as detailed, more articulated, come with more accessories, and are more affordable. Personally, I love the Bandai Creations figures because they are cheap and easy to find and still have very good quality. The Bandai Japan Movie Monster series figures are also very nice and come at reasonable prices even as imports.
"When man falls into conflict with nature, monsters are born." - Professor Hayashida, The Return of Godzilla