The way I see it, there are basically two type of RPG players, Pre-FF7 and post-FF7. Prior to FF7 RPG gaming was not really that big a segment of the gaming population, relative to other mainstream areas like platformers or sports games. When FF7 was released it was a marketing blitz of epic proportions and the setting was retooled to a futuristic sci-fi universe. Hundreds of Thousands of gamers who did not even know what exactly an RPG was ran out and picked it up. They were exposed to a gaming style they had never experienced before, and thus a favorable imprint of the genre was placed upon them. As is the case with most new things you like, the first time is usually the most memorable, and most well remembered of the experience. Lots of people automically say "FF7" because it was the game which brought them into the genre.
For instance, even though the battle system is shallow, my favorite RPG of all is the original Super Mario RPG, partly because of the humor involved, and partly because it was my first RPG.
That, and there are just people who inherently hate anything that is popular. PS2 #1, PS2 sucks. Metal Gear Solid is highly praised, MGS sucks. PC's outnumber Macs, PC's suck. People such as these especially hate it when something they like moves from underappreciated or niche into the mainstream.