hmmm I just wonder would a cleric that can cast spells the way a sorcerer casts wizards spells (ie limited spells available but doesnt have to memorize) a good class?

Yes but it is not a legitime class.

In 3rd edition, good clerics can spontaneously cast cure spells... ie, they could convert a previously prepared first level spell like Armor of Faith into a Cure Light Wounds spell, or a fourth level spell like Free Action into Cure Serious Wounds. Evil clerics can convert spells into Inflict/Cause spells (Cause Serious Wounds and whatnot)... Other than that, I don't think a class like that exists. If it *did*, it would be incredibly powerful, though. Perhaps too powerful.

actually, I think sorcerers are "priest type of wizards" in the sense that they're more like gainning spells as they level up rather than learning spells from the scrolls. Just like cleric and druid; they don't learn spells, as they level up, they gain new spells. The difference is that clerics have access to all cleric spells but sorcerers cannot do the same for wizard spells; however, sorcerers have advantage casting spells more creatively (don't have to set spells into slots).

So you think if such class existed it would be more powerful than sorcerer? (lets assume same number of spells per day).. the priest would be without as much very good offensive spells without simulacrum, without sequencers... and with less protection spells (PfMW, PfNW, PfME)

Well, let's assume for a moment that ToB is not installed, because Improved Alacrity makes the argument moot.
Let's talk equipment. Can they use the Robe of Vecna? If not, that's another strike against the cleric-sorc.
As for good spells to cast...
Doom; Symbol, Stun; Heal; Harm; Flamestrike; (Un)Holy Smite; Sunray; Shield of the Archons; Animate Dead; Gate; Fire Storm; Physical Mirror; Blade Barrier... And sooo many buffing spells.
Do they get druid spells? If so, then we should mention Iron Skins, Nature's Beauty, and the insect-related spells.
Maybe not more powerful than a sorc, but perhaps enough to stand toe to toe with one.. until they cast SI and PfME...
So perhaps I was wrong. Perhaps not. Either one would blow the other classes away (Except perhaps the Cleric/Mage), it's just a question of which of the two (or three) is more powerful.