Yup i LOVE replaying video games. I just started to replay Monster Hunter after a year. Put another good 70 hours into it so far but I tend to replay games often. It seems that I replay them when i forget some of the story and I have to replay it in order to remember. As for a game I've replayed the most, Megaman Legends 2. I cannot get enough of that game. I could pick it up right now and go for a week-long marathon. Also, i replayed Tomba 2 (if any body even knows what Tomba is...) and yes, I looked though walkthrough in order to find the last thing that i could never find no matter how hard I looked. It always made me mad when I was young but when i discovered the magic of the internet at a later age, my question was solved.
As for your later comment I too start as a content tourist. I play for the story, but not on easy. Always go normal. Then when I am though, I play to unlock and discover every single thing and beat it on the highest difficulty. For example, in Radiata Stories, there are over 150 characters you can recruit, and you can't do it all at once. I had the strategy guide but it still takes a crapload of time. I like to do this with most games. The problem is at that point, i am usually bored and move on to the next.