Eh, technically speaking, Emerald is harder than Ruby and Sapphire.How much harder is it to RNG on Ruby/Sapphire than on Emerald?
Or more specific is it worth to buy Pokemon Emerald?
By that, I mean that shinyness is next to impossible to do on retail in Emerald and good spreads are somewhere in the millions. Ruby and Sapphire are reasonably "easy" to RNG. It's just timing. Like, with a dead battery, getting a TID/SID that works for a spread takes like a minute or something per reset, since TID and SID are combo's and after you have a combo that works, good spreads aren't too far away. And perfect spreads aren't terrible either, assuming you use live battery abuse. My Modest 5iv spread in my Sapphire is somewhere around a 3 hour wait total I think? You just turn on the GBA, wait until the seed rolls around (this is on the minute, so very easy to time), then reset the game and wait until your frame rolls around. This is the tricky part, but like I said, it's just timing and if you fail, you just remove the battery and insert it back to try again. You don't need to wait weeks/months like in Emerald.
Of course, if you're talking about emulators, none of these are very difficult. But I assume you're talking about retail since you want to buy Emerald. Honestly though, you should buy Emerald anyway, because of the move tutors and the possibility of cloning your Pokémon in the Battle Frontier.