I haven't been in about a year, but in the last five they've added a couple of decent rides. The two most recent that I am aware of are the Batman and Superman rides. Batman is one of those foot-dangling roller coasters, and it's definitely a park favorite now. Superman is the latest edition, if I recall correctly, and it's a "free-fall" ride with quick acceleration and plenty of drops. I can't remember if the Titan is older than 5 years or not, but it's long and smooth high speed mega-coaster. It's pretty awesome. I think I actually remember them having to slow down part of the ride because of blackouts
The Six Flags in San Antonio is called Fiesta Texas. I went there quite a few years ago, and remember thinking it wasn't nearly as exciting as the park in Arlington.