>>27724204>itemsHeld items didn't exist in Gen I, and by extension, items as a whole weren't present in any PvP.
>the statsGen I had a single Special Stat, instead of Sp.Atk and Sp.Def. This led to special attackers being the focus of the meta, especially with shit like Amnesia, which would be the equivalent of two Calm Minds in one turn.
>IV'sRanged from 0-15, rather than 0-31. Since breeding didn't exist at the time, there was no reliable way to get good IVs.
>EVsEvery stat had Stat Experience, ranging from 0-65335. This functioned like modern EVs, but each stat could be maxxed out, like having 255 EVs in every stat nowadays, which would be impossible. EV training was also different, as Stat experience gained from a Pokemon equaled their base stats.
>some moves were physical, some moves were specialWhether a move was Physical or Special was dependent entirely on it's type. Fire Punch and Flamethrower were both calculated using the Special Stat, and Body Slam and Hyper beam were both calculated using the Attack and Defence Stats.
So yeah, gameplay-wise, a lot has changed since Gen I.