I can't think of any game in the series that I've played to completion that didn't give me at least one Game Over. It sounds like I skipped the easiest entries in the series, though (FFVIII and FFXIII).
FFX is mostly easy but there are one or two difficult boss battles (Seymour Flux and Yunalesca come to mind), although a case could be made that those battles are so cheap that they count as Fake Difficulty. FFVII gave me trouble at the Demon Wall and one other boss battle of which I've forgotten the name. FFVI gave me trouble at several points but that's mostly because it was the first JRPG I'd played in literally ten years (I'd played FFIV shortly after it came out). None of these games are particularly difficult in general but there are one or two tricky parts.
I do agree with Colonel Angus that FFV is really easy if you learn all the jobs. But then, even the hard version of FFIV is easy if you're overlevelled, and that's generally agreed to be one of the most challenging entries in the series.