i only got an ibanez rg370 and in my opinion it's a very good one. a friend of mine got a JEM and the says my rg is not far away from it although it costs only 400 euro ( his jem was 1300 euro).
but i think i got to try a jackson before saying they arent as good as ibanez ;)

ps: i didn't buy it because it had ibanez written on it :-P