I really enjoyed Final Fantasy XIII, though it may be because I haven't completed any of the other Final Fantasy games I've played (IV and VII), which as other have said, are just as linear - your progress gets stopped by needing a car, a boat, an airship and so on. It kept me entertained from beginning to end, however now that I've completed the story and don't have any particular goal minus 'Level Up' I have lost interest in the missions. I did about 30 or so before going on from Pulse the first time, and really enjoyed it then, but without that sense of purpose to them they get kind of old.
Eternal Sonata is just as linear!
The battles, minus the characters loving to group up so that everyone gets hit by Area of Effect attacks, where entertaining, and at times for me, challenging. I'm not sure how folk managed to get through it by 'Just Pressing X' as whenever I found myself struggling, it was mainly because the AI was doing a bad job, and it basically just uses the auto-ability system.
I completed the story around the 50 hour mark, and in terms of value for money compared to many of the games I own, this was very good. I didn't skip any of the cutscenes, and fought anything that I thought was a good trade off of time versus difficulty (those Cie'th that case the Inertial Barrier...oh how I hate them). Everyone is entitled to their opinion of course - a lot of games such as Dragon Age and such that folk rave about, I have no interest in, and at the same time I still enjoy RPGs such as Morrowind/Oblivion and Fallout 3.