Remember that game you exclusively played for months or even years? Share it here. I'm sure we're full of the good times that we can no longer experience.

For me, it was between Runescape and Halo 2.

A funny story is that before I even knew about Runescape, I played about 10 minutes of it when it was still in Classic. Probably a year or two of even fully playing it. I found a way to play Classic when Runescape 2 (the 3D one that's known mostly today, even though Runescape 3 is out and that's a major disappointment) and had a nostalgic moment that I remembered the starting area when years back.
I first got into Runescape in about 2003-2004 and played it until about 2011 when I quit. I was led into it through an odd sequence of events. Back to the old times of 2002 was the MSN Groups, which was my first forum experience. I was active in some Yugioh chat group there and they told me about a website called HabboHotel.co.uk (Yes, this was purely the original UK domain years even before the .com domain existed that's popularly used today). Months into Habbo I had come into conversation about a game called Runescape.
I had zero idea of what they were talking about even though I did butt in and they asked me what my mining level was... I was confused and lost, so I said something like level 46 or 60, something like that. A few weeks later I had looked it up and found it was some MMO, my first one at that, years even before WoW came out. I pretty much played it every day after school until 2009 when I moved.

Halo 2 was somewhere between 2007 and 2009 before I moved. Halo 2 was actually broadcasted on the USA network with MLG and plus my friends and I used to always go over to his house and play it. I asked my mom to get me an original xbox (probably a year before Halo 3 dropped. I remember my friend getting Halo 3 when it first came out and helping him set up his LIVE account so we could play together that night). Halo came together with me meeting some cool people, which I have no current contact with, but cool nonetheless. Halo 2 montages were popular then too so I used to always view those in my free time.