I don't use RT since the rating system is bizarre. Personally I thought IMDb had a more consistent rating system between critics and users than RT. IMDb still has a better system than RT, but personally I think it's been borked when Amazon bought them.
I actually agree with most of IMDb's ratings. The unusual high rating of a movie boosted by fake accounts or by "friends" of the filmmaker are easy to spot. That's why IMDb increased the voting count from 1,500 to 10,000 for a rating to be accepted in their "best" or "worst" lists. That said, I have my own rating code based on IMDb's ratings:
6,9 and higher - 10/10 or 5/5 (Perfect)
6,4 - 6,8 - 9/10 or 4.5/5 (Excellent)
5,9 - 6,3 - 8/10 or 4/5 (Great)
5,4 - 5,8 - 7/10 or 3.5/5 (Very Good)
4,9 - 5,3 - 6/10 or 3/5 (Good)
4,4 - 4,8 - 5/10 or 2.5/5 (Flawed but Worthy)
3,9 - 4,3 - 4/10 or 2/5 (Fair)
3,4 - 3,8 - 3/10 or 1.5/5 (Barely sufficient)
2,9 - 3,3 - 2/10 or 1/5 (Poor)
2,4 - 2,8 - 1/10 or 0.5/5 (Very Poor)
2,3 and lower - 0/10 or 0/5 (Awful)