How similar is the X Series & Eve Online? I'm thinking about buying the X Series from Steam if the X Series is like Eve Online but single player.

Well ... I've never played EVE online, but from what I understand, it's basically a player-ran world. So if by 'singleplyer' you mean 'NPCs instea of players,' yeah, it's fairly similar. I'm sure gaming systems differ a lot, but the point is: You can do whatever the fuck you want in X games, especially the latest installment (which has all content from previous games + it's own.) You can be a hunter, you can be a pirate, you can be a merchant, you can end up owning a goddamn empire built from a scratch. It's all up to you. Also, get a good book to have something to read while waiting for events to unfold. You'll be doing that a lot. That doesn't mean it's boring tho, it's just slow, especially when going the merchant route (and ... well prepare to give up real life. All of it.)

Which is the reason why I stopped after X2 (I still own all the games on Steam). I didn't have any more to give.

As for OP, I also don't have any experience with EVE, but from what I heard about the ability of players to control the world around them (and destroy it if you're a donkey), the X series is what you're looking for. At one point, I tried out different paths, used different mods and not once did I get the same experience or got bored doing things. I'd personally recommend you do NOT take the merchant route. Sure, once you set up your first factory complex you'll be more or less swimming in credits, but up to that point things can be rather uninteresting. I find that buying police licences or finding easy kill&good payout missions to be an excellent way of getting your basic money supply to expand your fledgling empire (just stay on the right side of the law. The police in the X universe is very effective, especially when you only own a fighter).

u can mine veld, ekhm nividium similar (hulk-way)... check
u can build own pos... ekm station's... check
dynamic market... check
grindy missions... check
galaxy connected by gates... check
epic ar, ekhm, plotlines... check
6 races (4 playable) with subfactions... check
zylion ships to try and fly... check

yea, it is similar :)

protip: stay away from x3: reunion (bugged like hell) and x3: prelude (very short). x2 or x3: tc is the best part to start the adventure with egosoft series.

Eve is a player driven game 99% of that game is controlled by the players both the market and the game as a whole. It is focused around PvP. But dont think thats always combat pvp. Playing the market is competion between you and someone else who wants buy or sell the same thing.

Mining ore is pvp cause another miner might steal it from right under your lasers (or more likely blow you up for shits and giggles)

PvE missioning can be PvP. Cause some ass like me might scan you down and loot and salvage your missions hoping you aggress so you can warp a fleet on them and pop their mission boats.

So... its a bit different. If you want an eve 21 day drop me a pm with an email address to send a trial to.

It's also quite different from X in the fact that, Even a few smaller ships can take down a high class ship in EVE with the right equipment. You don't see that happen in X. I remember my 14 day trial, I spent it running with a group of people taking out destroyers and battleships. I stayed at a distance in my ship (it was one of the smaller classes) with my Overpowered long-range rifles. Out of the other experienced players I was dealing the most damage (I had a ship specifically built for battles.) The moment i joined the group was quite special too. I battled the obviously experienced player in a 1 on 1 PVP For about 5 minutes and only just lost the battle, So he funded me for a new ship and invited me to his group ^.^

You can take down Carriers and Destroyers in fighters in X3 if you have experience. It's probably even easier to do than in EvE since combat is based around player skill in aiming/piloting and not dice rolls. Unlike EvE each turrent/gun on a ship has a specific and independent firing arc that it can fire in and each ship has unique deadzones that can be taken advantage of either by you or the enemy firing at you.

Every time I tried I got gunned down in an instant. I've heard they have several weakspots though. I mainly played the merchant path in X3.

You can kill cap ships in eve in frigs too depending on the opponent. Friend of mine hero tackled a carrier in a t2 frig. The cap pilot was dumb. He launched drones to kill the guy but set his smartbomb off to kill the frig too. He destroyed flight after flight of his own drones. The frig had enough dps to break its tank (shit fit too fyi) we called in support for speed but the frig would have won eventually unless it ran out of ammo. So it is doable just relies on what mmos have in bucket loads. Human stupidity

In the X series you can just ram your carrier into a weak frigate and destroy it from the collision :)

or nuke it from distance or find a blind spot and burn the Q with plasma... or, yea it is possible.

I've spent 227 hours in X3: R, think it's fine :)
Or just mob whatever u in path with 60 M3 fighters. :D

It's not "a bit" different. It's totally different. In X you control the ship yourself, and in EVE you basically give it instructions it vaguely follows. This pretty much changes everything. This lack of control bothered me, personally.

A big advantage of X3 (Reunion/Terran Conflict/Albion Prelude) is moddability. There are a lot of great mods, improved scripts etc to be found on the official forum (forum.egosoft.com). You'll have a hard time doing this if they use the MARS turret script, I think.