Corrected entry: Although the one of the two thieves at the beginning wishes never to have been born (which is granted by the Wishmaster), some scenes later his girlfriend is looking at a photograph which shows him. The photograph should have disappeared too.
Corrected entry: In the burglar scene in the beginning of the movie, the guy tells wishmaster "I wish I'd never been born" and he grants it. His girlfriend mourns him. But if he was never born then she shouldn't be upset over his death, because she would never have known he existed.
Correction: Already answered by another correction. The burglar's age was reversed to the point beyond when he was born. He was not literally erased from history, the wishmaster just granted his wish in a different way.
Corrected entry: One of the thieves robbing the museum wishes he was never born. His wish is granted, but the movie should have ended right there. Since he was never born, the museum would have never been robbed, there would never have been a shoot out that damaged the statue of Ahura Mazda and caused the "fire opal" to be found, hence the Wishmaster would never have been released. (00:06:25)
Correction: You say it yourself - ONE of the thieves, plural. The other guys could have done it without him, or another of their friends would have completed the party.
Correction: Remember that the Djinn often doesn't grant the exact wish that his victims make - indeed, if he had done so here it would have caused a Grandfather Paradox. Instead the Djinn took a different interpretation of the wish and reversed the thief's ageing process beyond the point where he would have been born, killing him without deleting him from history.