Hmmm, there's a lot of truth in these characterisations in general. They certainly hold true for a lot of popular and genre fiction as the stereotypes fit people's explanations very nicely. However, I do feel an obligation at this juncture to reference the lengthy fantasy novel(s) I'm intermittently working on myself. There's almost a full Mbti range of characters overall, but featured among the major ones are:
A truly evil and disturbed INFP (possibly INFJ, but INFP fits better). Main villain of the first part. Controls people by sophisticated, underhand psychological manipulation, and is extremely skilled at playing the victim to gain sympathy when her plans are thwarted.
A good ENTJ, actually the strongest of the good characters, in the first part at least. Not the most preposessing or easy to sympathise with though, due to a tendency to be blunt and outspoken, and believe people fools.
A good INTJ (high Fi though, she could easily be mistaken for INFP if you weren't paying attention). Utterly comitted to doing right, but has a somewhat idiosyncratic and creative interpretation of how this can be achieved, which makes her actually very effective. Not always the most personable of characters. Like the ENTJ, needs to be better judged through her actions than mode of speaking.
An ESTP tragic hero, who uhesitatingly stands up for what he believes in when no-one else will, a very positive example of the type but doomed to fail due to being too impulsive and not thinkng plans through. The arch-enemy of a very negative (self-indulgent asshole who engages in constant one-upmanship) example of the type.
See? It can be done! Mind you, I did make the heroine an ENFx, but we can't have everything, now can we?