My favorite would have to be Ruby & Sapphire. It will always hold a special place in my heart because me and my brother would play it together(well not "together" but on different GBA's and pretend that we were.) We would go around finding all the bases and make homes in them, we played around riding our bikes, we fought Groundon and Kyogre together, found Rayquaza, the three Regi's.
It introduced Mudkip, oh yeah the contest thing(don't remember what's it called) and the very first dragon Pokemon that I actually liked being Salamance(I don't hate other dragons it's just that they were overused, I'm looking at you Dragonite!) So yeah, Ruby & Sapphire has sentimental value to me.
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Autism is a disorder not a personality trait!
"God grant me the serenity to accept the things I cannot change,
Courage to change the things I can,
and Wisdom to know the difference."