I want to play the most complicated and strategically rich positions. The Ruy Lopez leads to such positions. The complicated positions are the most fun to play. 

Roger Williamson wrote on 03/19/11 at 13:36:42:


I am reminded of what John Nunn wrote in Secrets of Practical Chess:

There is  a wide range of possibilities to choose from "(...). All these are viable lines, so there is no need to panic. They all lead to the same general type of position, so that the experience you have gained with your former line will not be wasted. The general principles governing play with these Tchigorin structures will still be valid in your new line. Moreover, all the effort you have put into leaning how to combat earlier deviations by White will remain valid. Instead of facing a major overhaul, only a minor modification will be necessary" 

This raises the question: why play the Lopez as White? One answer from the Dutch coach IM Merijn van Delft:

"Many people are reluctant to take up the Ruy Lopez as White since there seems to be so much theory you have to know. But in fact the amount of theory you need to know to get started with the Ruy Lopez is quite limited. Essential knowledge includes something against 3...f5, something about the Open Spanish, knowing what the Marshall is and how you can avoid it, and the basic knight manoeuvre Nbd2-f1-g3. Model games can teach you a lot of ideas and a typical classic is Fischer-Shocron, Mar del Plata 1959 from My 60 Memorable Games. 
(From a note in Chess Vibes Openings).

I moved this here because it really is about repertoire considerations, not the Spanish per se.

I disagree with the premise of the OP that the half-open systems are easier to play than 1...e5.   Quite the reverse, I think.

Playing 1...e5 is probably the most solid way to meet 1.e4. White's play against this is based on the idea to remove the e5-pawn and get a majority in the centre. The direct ways to do this are 2.d4 and 2.f4 - both are playable but should not lead to an advantage for White. Therefore White usually goes 2.Nf3 (sometimes 2.Nc3 to follow up with 3.f4) and Black now can protect the e5-pawn with either 2...d6 or 2...Nc6 or play for counterattack with 2...Nf6. 2...Nc6 asks White the question: "How are you going to continue to play against my e5-pawn?" One way is the Scotch with 3.d4 - theoretically and practically speaking Black is IMO more than OK at the moment with the Mieses Variation (because White has to slightly overexpand himself with the e5-move). Another way is to play a somewhat "neutral" move with 3.Bc4 and either slow down the play or try for an immediate attack (mostly against f7). If Black goes 3...Bc5 White may return to the idea of central dominance by playing the still dangerous Evans Gambit with 4.b4 followed by c3 and d4.

After all the mentioned moves and variations (from Kings Gambit via Italian to Scotch) somehow miss White's main idea after 1.e4 - to play against e5-pawn. Therefore we arrive at 3.Bb5 - the Ruy Lopez. Surprisingly 3.Bb5 does not immediately threaten to win the pawn with BxN followed by Nxe5 because of the counterattack ...Qd4 netting the e4-pawn.

And here we arrive at the beauty of the Ruy Lopez - White is trying to play for long-time pressure against e5 or forcing Black to play e5xd4 at some convinient moment. On the other hand Black has nearly a free hand to choose a variation - he can play very sharp lines (starting from 3...f5) or very solid ones (e.g. going for RL-Main-Line or the Breyer).

So why allow White to play the Ruy? Because as Black we (often) have the choice of variation - we mostly will be better prepared. If White really wants to "torture" Black he has to go for the main lines - if he deviates (e.g. with Qe2 or d3 or Bc6) at some point, play usually is less critical and tends to become equal.