It would be impossible to discuss all model kits, even from a single manufacturer, which is why it's easier to discuss and review a single kit or a group of related kits (say, AMT's Trophy Series kits). Quality can vary, even within one manufacturers catalog. For instance Revell kits on the early '80s were not very good, but some of their early and mid-'90s kits are excellent.
As always, opinions will vary.