The problem is that, as you say, it doesn't make for fun bosses. Although I'm inclined to think that, with a bit of creativity, they could have improved on those. They could have made the enemies' patterns more complex, or involved environmental factors, or made the objective to dodge the bosses' attacks while attempting to reach certain checkpoints scattered throughout a large room, or something more involved than a single boss in a single-screen empty room.
But they DO do that, and for a game from 1990, they do enough to keep me interested. I'll put it in spoiler tags for people who haven't gotten there yet, but...
The very first boss in the game has environmental factors. The boss itself won't hurt you at all, but the fire pillars will. So you dodge the fire pillars and attack the boss whenever he appears.The two masks is a very interesting boss battle. They both have protective orbs surrounding them, and you can only hurt the orange one. So you attempt to attack the orange one, while at the same time dodging the orbs. And then the masks will switch places. Sure, they're patterns aren't that complex, because they're symmetrical, but let's be honest, I think people would be complaining a lot more if that boss battle were overly complex. Then it really would be very hard.The last boss in the game is plenty complex and gets even more complex as the fight continues. Every time you hit him part of the arena is taken away, giving you less room to maneuver. And first there's one orb trying to attack you, and later there's two. Once again, if the pattern the boss followed wasn't at least somewhat predictable, the boss would be a lot worse.If the boss battles had more indicators or feedback to the player I think that would go some way towards resolving the problems that people are having with them. Jokes are often made about the fact that boss battles in video games often have glowing sections on their bodies, or giant eyes, or an exposed underbelly etc. The use of those types of indicators are perhaps a little trite, but at least they feedback information to the player. When games fail to provide that information they can become really frustrating for some people.
I kind of agree and disagree with this. Yes, the bosses had little indication of where to hit them, but that's because, for most of them, their entire body is where you need to hit them. Its just a matter of when. There are a few exception like
the centipede boss, because he is attacking with a part of his body, therefore you must attack the part of his body that is not attacking you.
But even then, its pretty obvious that you should not run into the giant pincers trying to bite you, but instead hit his backside But most of the bosses do not attack you with their bodies, but with something external, meaning whenever you do get the chance to attack their bodies you know you can do it without getting hurt. And whenever you land a successful hit, the screen flashes, you here that "hit" sound, and you see their life bar go down. That's a pretty obvious indication that you're hitting them at the right time.
Now, this does take some time and some experimentation, but that's not a bad thing, is it? Besides, at least this game encourages experimentation. Like I mentioned earlier, if you have the heal ring and save right outside the boss door, then you can fight the boss over and over without wasting any time. You don't have to save at a save point and slog all the way back to the boss door. That would discourage experimentation. With the system Ys I has, you can try several different approaches without being harshly punished for it.
So, do the boss fights have some issues? Sure, but I think they do plenty of things both outside of the fights and within the fights themselves to leverage those problems. In the end it makes for boss fights that are no better or worse than boss fights in any other game. And as far as this game is concerned, I find them way more fun then running around poor, maze-like level design, steam-rolling enemies with no thought.