EarthBound: Assuming you mean the Super Nintendo title (and not EarthBound Beginnings, the one released on the NES), it's a quirky RPG with a great soundtrack and a nice story. In regards to gameplay, I'd say it's not much different than any other RPG you might play; traditional turn-based battles, overworld movement, and so on. That being said, for story, humor, and music, it's worth checking out.
A Link to the Past: Although A Link Between Worlds is a sequel, I think it's unnecessary to play in chronological order; you could enjoy A Link to the Past without having played A Link Between Worlds prior.
Super Metroid/Metroid Prime: Excellent games! Other M is usually seen as the worst Metroid game (either that or tied with Metroid II as worst Metroid game), so if you kind of enjoyed that game, I'm sure you'd really enjoy Metroid Prime (which takes on a first-person shooter gameplay style, as compared to Super Metroid). Super Metroid is a very solid game, and is, to me, the epitome of what any other side-scrolling Metroid game should strive for. Its soundtrack is great, as is the gameplay; the game feels just right. There is a degree of challenge to it, however, but overall, I'd recommend the game if you enjoy platformers.
Donkey Kong Country: It's been ages since I've played Donkey Kong Country Returns. However, from what I recall, the gameplay isn't that much different (the difference, I'd say, is about as drastic as the All-Stars version of Super Mario Bros. in comparison to New Super Mario Bros.). As for story, DKC doesn't have much of one - it's simply "King K. Rool stole Donkey Kong's banana hoard, and now you have to go and get it back". Nothing spectacular, but the game itself is very enjoyable, so it's no big deal.
If your preference lies in RPGs, EarthBound would be my suggestion - but, the game doesn't necessarily contain a lot of action or collecting. The story is enjoyable in my opinion, and there is plenty of different locations in EarthBound (as to whether or not you'd consider it a lot of exploring or not, I'm not too sure). If you enjoy challenge, then I recommend Super Metroid. Donkey Kong Country isn't all too challenging (at least in comparison to the second game), so if you'd prefer a more leisurely platformer, I'd choose DKC over Super Metroid. Finally, A Link to the Past: it's a great Zelda entry, so if you've enjoyed other games in the Zelda series, this is definitely one I would recommend.
Apologies for the lengthy post, but I hope it helps!