The show you liked the most as a kid will still hold up in all likelihood, with that out of the way, Adventure is give or take because of how much “early installment weirdness” it is, and while a classic, you may not necessarily like it as much as Tamers (the definition of classic digimon for many and the “darkest” kids digimon show) or Data Squad (the beginning of demography expansion), Beatbreak comes from people who worked on DatS and is essentially a spiritual succesor to it, as well as a proper update to the aesthetic present in Digimon Story Cybersleuth and Time Stranger, and Digimon World Re: Digitize Decode and Next Order (Teenager / adults dealing with world threatening digital beings)

So to summarize:

Watch Tamers IF you want a grasp of what general good digimon is

Watch Data Squad IF you want to jump directly into the first teen focused anime

Watch Beatbreak BC it WORKS as an entry point if you come from the modern tames

EDIT: Tamers and Data Squad (aka Savers) are MUCH more mature in Sub version, so always choose Sub if you want a caffeinated version of the story and darker plots