The complexity of the game hooked me when I first started out. Mining for example seemed to be the easiest thing to get into yet is so deep that it requires heavy tinkering with your "build" as well as some research in order to yield optimal results. I mined my first asteroid after 10 minutes of jumping into it, became GOOD at mining 2 months later I think when the required skills finished enabling me to fly the "real" ships and after that finetuning and optimizing continued. I was in awe before this as mining (tho critical factor in the game) is THE most scoffed-at activity you can do (the playerbase ridicule and mock miners). When I got bored of mining I was thinking about adding to my activity portfolio and planned ahead, finally set myself on mission running and that opened a whole new world of options and possebilities. The variety in ships is awesome (and many of the designs are simply breathtaking). The balance is constantly worked on and doesnt squeeze you into a single way to do stuff (FOTM). YOu have CHOICE and FREEDOM in how you approach things.
It can be all pretty overwhelming so being in a helpfull corp helps tons. I mean menu operation and finding the correct buttons in that cast flood of stuff is a challenge already. But thats what I found so incredibly fascinating.
I worked up my mission ranks, upped my ship types to Battleship (pretty much the end before you delve into hardcore endgame) and participated in my first fleet operations aiming to "rack in the dough". Boy was that NOT fun at all. I was so excited and hyped about it all and then it was a complete disappointment. The pressure, the tunneling into a certain view in order to be effective, no freedom in fitting at all, you either have the required gear or you are out and the overall tone in those fleets. You can have some nice groups but overall most of these people have run missions ad nauseum for years now and have lil to no tolerance for newbies or mistakes and they dont hesitate to tell you how much you su*k.
PvP...is pretty much the same basically you are forced into playing the game at max zoom-out in order to keep your overview and rely heavily on micro-managing for efficiency. Its too hectic and too forced for my taste, I never really enjoyed it. That left me with the "passive" activities which can be fun but after 6 months you run into the skill-wall as in any meaningfull skill-up takes weeks or even months to complete leaving you with the same old same old activities to run which you cant stand anymore. When I noticed that I pay my sub simply to check my skills every couple of days then log off (because ingame money wasnt an issue anymore) I stopped playing alltogether.
Usually games start slow and ramp up in speed when you aquire new skills, options, unlock areas etc. EVE is kinda the other way around. It starts out strong and after a while everything slows down. Due to its age there is nothing to explore or discover anymore. All the synergies and optimal ways are posted and analyzed a hundred times over. Thats what really put me off and prevents me from jumping on again.
edit: it might read like a crushing review but really....I LOVE EVE, its an awesome game, it just turns stale after a few months if you are not into PvP (I am not) but even if you are you ll probably get bored after a few more months. I still respect the game as a whole, how it grew over time, the internal beauty (structure) of it all, the player-driven economy. Simply B-E-U-tifull.