compelling story, 2 new types, non-linear, addressed psychic being too OP, great pokemon design, introduction of breeding, literally has 2 FUCKING REGIONS (a feat never repeated), ability to fight protagonist from previous game. 2 of the best eeveelutions introduced, day and night cycle, It goes on an on.
Interesting question. Most of the time I chose Squirtle or Charmander. I was always more partial to Charmander, but Squirtle holds his own. Because of that I like to pick Bulbasaur now as I've neglected him for too many years. I love Raichu, but he doesn't really compare to the 3 starters imo.
Type: Null, kinda gimmicky, but somewhat interesting. Lycanroc, not a bad design for a later gen game. I did beat SUMO, but only played through it once. I had fun with it at the time. Haven't gone back since then.