Natures and abilities

Do you like the introduction to these 2 gameplay mechanics?

The only thing I like about replaying Gen 1 and 2 is that you could just catch a pokemon and not care about their nature. Pick and play so to speak. I do love abilities though; Greninja with Protean and Cradily with Storm Drain are epic.

Hell. Yes.

Abilities and Natures have affected Pokemon in both the in-game and competitive department, and makes the games a lot more fun in my opinion. I like trying to catch a Pokemon with a good ability, and abilities (particularly Hidden Abilities) are what make me love things like the Friend Safari. As for Natures, they help a lot with competitive battling, something I'm really into. I also like to play Gen 1/2 games due to the lack of an ability - relying only on stats and abilities is a fun thing for me.

Well, Yukari said little different from what I was going to say - abilities really change up how certain Pokémon are used and added a massive overhaul to battles. Natures, however, I don't mind them, they do give nice bonuses to things that are one-sided on attacking, but yeah when playing through you may be that guy who needs his Pokémon to not have s*** natures. I tend to be that one. In normal playthroughs it's not as much of a deal, but in challenges (especially Nuzlockes and Wedlockes) it can get jarring coming across, say, an Adamant Abra or Litwick or a Modest Fighting-type.

In-game, natures and abilities don't exactly matter. This allows us to use whatever Pokémon we feel, without having to worry about winning, losing, or anything else that might seem a bit too complex. All you'd have to do is train your Pokémon enough, and if they're at some good level and have access to decent moves, you're bound to win battles whether if you actually try or not. It's how the system was designed, really.

However, when it comes to competitive battling, I feel that it's much, much more different; here, they do matter. Abilities could give you chance to gain an upper-hand at any time, and could even save you from losing a match. Some people even rely on them entirely; it's their strategy. One, quick example would be using Drought to give all your fire- and grass-type team-members an advantage over opponents.

As far as natures go, they also matter. Competitively, every single stat counts, and if you're looking to maximize any one of your Pokémon's stats as much as possible, utilizing natures is mandatory.