Gen I
>Physical/Special based on type
>EVs are uncapped.
>Special stat covers offense and defense

Gen II
>Physical/Special still based on type
>EVs still uncapped
>Special stat split into Special Attack and Special Defense

Gen III
>Physical/Special still based on type
>EVs capped

Gen IV
>Physical/Special is move-specific
>EVs capped

So many Kantomons have gotten fucked by this because their stat distribution is flat.

Under the old system a Pokemon having level stats with a decent BST was a benefit because they could max out anything they wanted to and be powerful with attacks of all types. The "min" of min-max did not exist.

Under the new system Pokemon have to be raised with a specialization is mind for optimal performance. As a result, the best Pokemon have to excel in some stat and the old "master of none" types which were an asset in the first two gens (especially the second gen) are now liabilities.

Despite the changes to the battle system and the radical difference in what makes a valuable Pokemon, the Gen I and II Pokemon have not been rebalanced to compensate. That's why Kanto especially is so full of shitmons.

It's a pretty big fuck up.