Didn't you keep certain weapons and armor? Making the second replay faster and easier? I just played the Genesis one, so not sure if this is in every game.
You dont really keep anything in GnG, certainly not armor if you get hit, its gone. The challenge in the second run is getting the special weapon which is needed to reach the finale boss level, without it you'll be booted back a level (thankfully its easy to get it in this level).
The issues with Ghouls can be:
Getting the special weapon early on isnt too difficult, you do need to get the armor upgrade first but there's plenty of chests in stage 1 to do so. And the special weapon is good... until it isnt.
See stage 4 is a fight against a creature which has a number of weak spots, and a couple are insanely hard to reach with the special weapon since range is limited on it. Makes the entire thing harder than it should. So honestly you either wanna swap weapons on this stage, or wait until stage 5 to get the special weapon.
Either way, its really not that bad, I felt the GnG games got a bit of a bad wrap for this in the early days, the games arent long and I didnt think any were THAT bad to clear. Now dont get me wrong, Super GnG has one annoying bit at the end with Asteroth due to, yet again a short ranged special weapon you need (no way round it this time like in GnG), and the latest game (Resurrection) is just legit hard on its second run through, but you can at least power up nicely as you go there...
But oh how I detest the original "best ending" in Ulimate GnG for the PSP. Basically, clear the game once, no problem (well, assuming the difficulty doesnt crush your bones). Second time round? Basically a "screw you, find all the hidden collectibles". I hate hidden collectibles lol. Its a pretty big game as well, especially as you need certain armors to reach certain places, and no guides really existed at the time to tell you where the darn things were... Still need to go back to that...
Thankfully Capcom themselves realised how shit it was so when Japan got Ultimate GNG Kai (an updated edition on the PSP), they basically remixed the entire game, tweaking difficulty, enemy spawns, and yes even the collectibles so you no longer needed them, rather just do the usual two loops. And it made the game so much better.