Fun Fact: You don't need to be an expert to beat Super Castlevania IV. Just power up your whip, get the boomerang, triple-shot it up, and then you're neigh invincible. Even if you get hit, enemies deal crap for damage. The only real worry comes from elements of instant death.
Lol, I thought I already posted here that the only thing that kills me in SCIV is instant death by falling in a pit. It's actually another reason why this game upsets me/bores me. To die in a lame pit and then be forced to do most of a boring no challenge otherwise level all over again is enough to make me turn system/emulator off and forget about playing this game again. And since I never use passwords in my classic vania games, starting this game all over again next time I start is a drag (lol, last time I started this game, I for the first time in my life sang out loud along with the first stage theme as it started; "Bored, bore, bore, bored, bore, bore, bored." Because honestly, that's how I felt and couldn't help but wonder as to why I'm wasting my time playing this?
And yeah, the boomerang item in this game is my choice weapon. There is absolutely zero point in getting any other weapon in this game unlike other Castlevania games. This sub-item is crazy way more usefull then the others. Two boomerangs is all you need to kill Medusa.

Only since I still die in some lame platforming related area instant death type thing, due to not playing this game enough to be familiar with it enough, makes powering up my subweapons pointless. Especially when all you really need for this game is you whip, really.

And the game is still easy enough with just the whip only... heck, when ever I have a triple boomerang, I still never use it during a level, but save it for bosses only, as utterly destroying them with the aid of a triple boomerang is fun.

Super Castlevania IV is sort of crappy in terms of challenge and polish. The level design very rarely pushes you to do anything difficult, enemies have needlessly high amounts of health while lacking the cunning to make them engaging, some bosses have unavoidable attacks or are easily trivialized, the whip-swinging mechanic is under utilized, the whip's range and aiming ability obsolete almost all of the sub-weapons and any semblence of strategy, the game has a raging axe armor fetish (And bat fetish for the second playthrough of the game), and the only enemies that are exploited effectively are the bats (occasionally), floating eyeballs and skeletons.
Lol, and people complain about overused enemies in the next SNES vania game. But yeah, I noticed the extreme bat fetish this game uses for loop two as well + they use them very cheaply, like you almost better know where they're coming from otherwise BAM! You take a hit... luckily this game supplies you with a ton of meat.

But yeah, lol, did I ever get bitched at in another topic with people complaining about the bats in Dracula XX for SNES & them being cheap. I guess them same people never payed Super Castlevania IV loop two before?

However, Super Castlevania IV is considered good because while it's level design isn't exactly creative from a challenge perspective, it combines colorful, detailed visuals with music to create a sense of immersion rivaled only by Symphony of the Night in the entire series. While it never asks for much in terms of challenge, it also has enough variation in the level design to not feel bland either. It's also got very flexible controls and mechanics, which makes it a very approachable game.
And here is why I'm having such a hard time liking this game. I didn't see any graphics excellence at all for the most part. Save for a few key scenes like when there is a lot of paralax background scrolls and small scenes like where you fight the Mummy boss & the final set of bosses after that.
Now add the fact that playing this game bores me gameplay wise. And it's really not that hard to see why I'm having such a hard time trying to get into this game.

I almost feel like completely giving up on this game sometimes from the sheer boredom this game gives me... Sometimes I think that if only I had played this game when it came out right away, instead of the tailend of the SNES' lifespan, that maybe I would of seen some of this game graphical excellence and that I too may of been a fan of this game? Now I feel very sad that this isn't the case and can only wish I had the same nostalgic memories as the Videogame Nerd and many other from this site who list this game as their fave... But as it is, when I first popped in this game I was like "Yikes & No! I wasted my money on a prehistoric, & very well looking it, SNES game.

EGM, you lied to me!"
Oh, and exactly, when people say a game has good level design, they almost never mean it from a challenge game design perspective, but from a visual perspective only.
I don't feel it's enough to get me to like the game a lot, but it's unfrustrating and immersive, which for a lot of people, is agreeable.
Yeah, this game's massive size really upsets me too since I don't like this game. But the sad thing is that if I did like this game, this game's massive size would of been one of it's best features, and one of the reason why I would of probably rated it as one of my most fave vania games ever... But I don't know, graphics alone aren't always enough I find. I thought SotN looked out of this world graphically back when it first came out (it was my second played and beat vania game), and since then I have yet to replay SotN even once more... But that's just me, as SotN is the other most popular Castlevania game out there... So I guess your right? Most people favour Castlevania games mostly due to graphics alone...