Well I think GTA jumped the shark as soon as GTA IV was released, the graphics bored me, they went for realism over fun ten fold. All the missions now had zero variety in it like the PS2 ones, and the story and radio weren't funny or entertaining or interesting at all.
GTA vice city and liberty city stories and vice city stories etc have so much replay value I can always play them. I sold GTA IV and the only reason why I bought a backwards compatible PS3 on ebay was to play the old GTA's. Just my Opinion but that's how I think of it.