There's plenty of games I've tried, liked, but were too stupid to play properly, and too stupid to realise this and give up.
Love the jagged alliance series and X-com, never got anywhere in them...I'm still stuck in the tutorial campaign for Deadly games (the minesweeping mission of it) yet I still return.
Robinson's requiem. Never got anywhere in it, but have died in lots of interesting ways.
Space empires V....I heard it was like Master of Orion for those who wanted an impressive depth. I'd like to add oppressive depth too. I spent 2 hours reading through the tutorial and playing it. Started a single player game and felt utterly and completely lost. 20 turns later I quit.
And generally any RTS game out there. I lose track of everything going on too quickly. Good thing I'm not as interested in them as turn based squad games, but I still find them intrigueing, as such my collection contains games like Warcraft 2, Starcraft, Supreme commander, Rise of Nations, Age of empires/mythology, Settlers 5....and the only one I've made it past the 2nd campaign mission in is warcraft 2.