That's it. I don't think it's easy to pull off good AI in a sidescroller, perhaps because it's such an artificial environment. Real world locations are horizontal rather than vertical. Good AI, for example, would suggest flanking, but flanking is almost impossible in a 2d world. Tactics that would work in a real world setting don't work in the made up environment of sidescrollers.. I think what we want instead is to just focus on interesting patterns for enemies. The other thing is, I don't want the enemies to automatically know where I am when I'm not on their plane, or there's a wall between us. They should think I am in the last location they saw me at. I hate that a skelebot stands above me on another plane and he knows exactly where I am so he stands right above me.
Iji was ok, but it was also very slow-paced and the controls always seemed a little restrictive. I found that one got pretty repetetive as well.
Loved the decisions in that game though. Very much System-Shock-like.
Spelunky, now, that's a pretty darn good game, but actually defeating enemies usually just involves stomping or using whatever weapon you happen to have at the time. And even then, in that game it was ALWAYS better to avoid them if you could; the only things that might drop something were the minibosses, and they werent all that tough compared to the rest of the game. The game is decently challenging, but alot of that comes from the area design, as the enemies all had braindead AI. Though that type of simple patterns work well for that game. Final boss was WAY too easy though.
Yeah the enemies were not the main challenge there, and they were high risk. But once I got comfortable with the game, enemies were fun to fight despite the fact that they were dangerous. You're right that they were mostly braindead (like most side-scrollers), but feeding cavemen to man-eating plants or throwing them on spikes never gets old
Also, again, the patterns were cool. Each enemy had a different pattern, and by learning the pattern you knew how to deal with them. I think a lot of that has to do with the fact that you couldn't just shoot in any direction. Being able to shoot at any angle and at almost any distance nullifies enemy patterns. What does it matter if you have bouncing enemy or an enemy that heads straight for you or one that comes up from underground? You point and click regardless.