I didn't do a speedrun like those who try for the records, however, I did do it in an attempt to finish my pokedex. Emerald running less than 7 game hours to Finish E4, to get my a Latias (which took another 7 game hours to catch as I didn't have a master ball used on Rayquaza), only to discover I could've just gotten it in Omega Ruby.... However, I didn't realize I didn't have a Kyogre so not a complete waste.
Then I realized after clearing white and White 2 I left some pokemon on HeartGold and SoulSilver I had wanted to carry into the new world. So I "Sped" through white which took me less than 10 game hours.
Both runs took me about 2 days, with the exception of Emerald as catching Latias for my Dex took me an extra 2 days. She was not nice at all.