*The controls are awkward. You can't change your direction mid-jump. This isn't different from, say, Castlevania, but the levels are designed to exploit this, resulting in frequent cheap deaths unless you practice (a lot) or memorize the hazards.
*You can take two hits before dying, even if you have the third-level armor.
*The weapons mostly only fire left and right, and enemies frequently attack from above and below.
*There's no save or password system, so you need to complete the entire (long) game in one sitting.
*Worst of all, you have to complete the entire game TWICE to actually beat it! The second time usually forces you to use a weapon that's vastly inferior to the best one.

Despite all this, the games are still fun to play in short bursts because they have that great Capcom quality and polish.

I haven't played much Halo lately. I'm doing a Four Job Fiesta run for Final Fantasy V ( fourjobfiesta.com/), which is an awesome and fun challenge mode for charity. The problem is that this year the organizer changed the charity from Child's Play (buys toys for sick kids, something that 99.9% of people can get behind) to a BLM-affiliated one. I already gave $5 to change one of my jobs because I didn't realize this (stupid, I know) but I'm going to give $25 to Child's Play as penance.