I loved the game. During the first part I was kinda disappointed but once I got the hang of materia combinations I loved it. So much stuff you can do. My only issue with the game is that you don't really need complex materia combinations to actually win. The way the game is made even simple use of materia is enough to get through most if not all enemies. So cool materia combinations would essentially be overkill. I have played all the PS FF games and they are all basically like that though, specially if you level up (except to some extent FFVIII where boss's strength was according to your level). Its a bit unfortunate most RPGs don't have an alternative to play a harder version of the game after you beat it on the first round. Imagine a FFVIII where actually going through the trouble of getting everything didn't result in the game being too easy lol(not the same kind of game but I loved the hero quest in skyward sword).
You are kinda right about ruby though... I did use a guide to see what the hell was going on when my two party members just disappeared. I just went with the daser trick and it was all too easy at the second attempt lol. Even then, I don't think it necessarily would have been extremely hard to win with just cloud. Putting a little more thought into it I don't think it would have been all that difficult to beat it. Emerald was actually easy though. Gravity attacks are not really a threat if you heal fast and its defense is not that high so even 4x materia did 40k damage every round (I kinda had 1 for each character at that point). I had cloud equipped with several counter materia, enemy skill and KOTR, even if that wasn't enough I could have just given him more counter materia and he would have attacked 10 times in between turns lol.
From what I gathered what you need a guide for in the game is not to actually beat bosses but rather to deal with the sheer amount of random. Many of the side quests are located randomly and so far out the progression of the game that I don't see how it would be possible to even find them if you went about it on your own. I got the gold chocobo but the game barely made a mention on how to get it, I still don't know how exactly you find out how to breed them to get the stuff you want. And even using a guide still you still need an offensive amount of time and money to breed a chocobo. If it wasn't for the selling of mastered all materia I would still be going at it without any sort of direction. I guess the chocobo sage is the one that is supposed to hint at how to breed chocobo although I never took the time to figure that out. And of course without a guide you wouldn't even have a reason to even breed chocobo and without one you wouldn't even know what you can get with them. Well, with my experience in other games I was able to tell on sight which locations were only accessible by chocobo however its not like you'd have a reason to go there if chocobo breeding was not to begin with an important part of the game. And chocobo racing sucks balls, I hated every bit of it, specially that damned black chocobo. I guess my biggest complain about the game (and all FF games I have played so far) is that the developers try to pass completely random things as if they were puzzles. Backtracking 3 continents just for the random chance of probably finding a side quest which might do something is not a puzzle (DAMN IT!). I love exploring the worlds developers make but to some extent the idea is taken a tad far with FF games (and that comes from someone that has beaten console zelda games an offensive number of times lol). Once you have the stronger materia in the game there is no reason for any of the bosses in the game to be much of a challenge (although I still kinda get the impression that the strongest materia combo would be phoenix-final attack, a bunch of counters and KOTR paired with a number of things). Counter as many times as you can fit the materia in along with the strongest materia in the game along with a couple mean heals from a healing amteria or enemy skills.