It all depends on your body. If you haven't seen abs since the 90's more then likely you need a combination of building muscle and dieting.
Ronnie's abs have great potential for growth compared to others. This is more of a curse, because you can't just do abs all the time or else they start to get too big and when not sucking in makes him look fat, but if he doesn't do them enough they start to lose tone and don't look as ripped even when flexing.
I like CT's view for people who have a tough time showing them. You need to build enough muscle to create separation and low body fat to show them.
Follow one of his programs pick a particular diet follow it for a 2 months and see your results.
just a though 20rm deads always seem to do wonders for my bringing out my abs, it's just tough to want to do them more then every few months.