You're correct. La Liga is the only consistent 2 horse race in Europe. Obviously by the end of the season you do cut it down to 2 teams with realistic chances in any league, but still, anyone outside Real or Barcelona have no chance in winning the league b/c they don't have the capacity to do so.
There are new challengers every season or so in the Premier League (Liverpool 2-3 seasons ago, Arsenal last season, City this season) regardless of how repetitive it is.
Serie A recently has had a lot of new challengers, or new faces. Napoli have come into it, as have Udinese, and possibly Juventus. The race for the Champions League spots in Serie A is much more competitive than any other league in the world.
The divide on opinion, though, is having a competitive league v a stable league. If you have a bit of both, then you have a fine balance, but many different teams win the Bundesliga and within 2 years can be nowhere near what they were (Stuttgart, Wolfsburg et al). Bordeaux have disappeared recently after being under-dog forces in 2009.
But I digress; La Liga is the only consistent 2 horse race in the top European leagues.