StarOcean on 13 February 2016
Best made in the series is HeartGold/SoulSilver. Recent ones worth giving a try are X/Y and ORAS.
Old ones to try are Crystal, FR/LG, and Emerald.
You can try R/B if you want, but if you have no nostalgia for them then by todays standards they're VERY rough games. If you're going to play an old school Pokemon game go for Gen 2 games. Much better polished and overall better quality than the originals
