In case anyone's interested in a bit more detail on why our pronunciations of Egyptian are so uncertain...
Languages evolve over time, and Egyptian was spoken in some form or another for around 3500 years. (A version of it still exists in the liturgical language of the Coptic church.) As a result, there's a lot of variation in the grammar and vocabulary of inscriptions and records from the classical period. The version of Egyptian Lockleed posted above is mostly Middle Egyptian as reconstructed by linguists over the last century and a half.
Structurally, Egyptian has some similarities to the Semitic languages, particularly in its phonemic inventory and its use of three-consonant roots as the basis of word structure. The writing systems (hieroglyphic, hieratic and demotic) usually represented only the consonants, with the vowels being implied by various means. As a result, we have a pretty good idea of what consonants were used in different words, but no clue what vowels were used between the consonants. In order to make it easier to discuss Egyptian, linguists adopted a pronunciation scheme to read things aloud without knowing the proper vowels. In general, glottal stops were pronounced as "a", j and y were pronounced as "i" (or "ee"), and w was pronounced as "u" or "o". If that wasn't enough to pronounce a word, they would then and an "e" between consonants. So the sun (and by extention the sun god "Ra") was called some word that had the consonants r' (r followed by a glottal stop). We just say "Ra" because it's the best we can do, accurately.
Throughout the 20th century, linguists made an effort to reconstruct the vowel structure of Egyptian as well, usually by mapping the Egyptian words that were borrowed into different languages with known histories. By figuring out what changes the modern word would've gone through to reach its current form, they can infer how it was pronounced when it first entered the language. Greek, Latin, Arabic, and of course Coptic have all been good sources, but at the end of the day it's still educated guesswork, so the "definitive" scholarly pronunciation remains the "Ra," even though it was almost certainly pronounced "Ri'u" or "Ri'a."
If you want to get an idea of what "real" Egyptian sounded like, take a listen to the dialogue in the movies Stargate and The Mummy. They both use a reconstruction of spoken Egyptian by an Egyptologist named Stuart Tyson Smith. His isn't the only take on it, but it's probably the most thorough and most accessible.