So from Red/Blue to Fire Red/Leaf Green etc.
Your question is extremely difficult to answer. After a quick bit of research i'd say that the trainers that are stronger are those who now have access to Mega Evolution. Wally also might fit the category but the reason i'm not including him is because his Gardevoir was changed to a Gallade which still Mega Evolves but in my opinion at least is slightly weaker than Gardevoir normally. Hope this answers your question.