Problem with the bosses is they are so simple, there's not a whole lot you can with them.
I found Kahn and Motaro way too easy in MK3 to defeat. I can own them with any character on any difficulty level. But in MK3 Ultimate, Motaro is a prick and so is that Douchebag, Kahn. But, I can still defeat them both. As you say, they are predictable as shit on your front lawn. :mrgreen:
One universal rule that works everytime on every single character, with every single character, except the boss and sub boss characters, is the crouch and uppercut. I have seen in past times in the arcades, this one move get people all the way to the end battles. Timing is CRUCIAL! Absolutely crucial. For example, in MK2, if you uppercut an opponent too soon, you will not only miss, but they will take advantage of you [no not in that way, lol]. Alternatively, if you leave it too late to execute you uppercut, the computer will just throw you. And in MK3 and all the other classic MK games, the crouching well timed uppercut will 90% of the time get you through. Though, I must warn you that it can get very boring doing it this way. But it's a handy strategy to learn and facilitate, nonetheless.
I've completed MK3/MK3Ultimate/MKT and MK4/Gold with every single character. You alwasy lean towards your favourites at first and play hard with them. Then you spread your wings a little by experimenting and trying out other players. When for example I started playing MK3, I almost always used Subzero. This was for two reasons. Firstly: He had the best disabling move [stun], the freeze. Then your opponent was at your mercy. Two: I knew how to use him effectively enough to make it through MK3 upon playing it for the first time. Well, not the very first time, but my first games. Later, I used others until eventually I had pretty much most of them down pat with all moves and stuff.
By thw way, Noob Saibot is the easiest character for me to complete MKT with. Rain is a close second, followed by Human Smoke. Ninja + Special Move = easy victory. Against the computer, at least.