In short, the world of 2007 is radically different from the world of the late 1970s. However, none of the major vendors have performed a complete redesign to deal with this changed landscape. As such they should be considered legacy technology, more than a quarter of century in age and "long in the tooth".
In every major application area I can think of, it is possible to build a SQL DBMS engine with vertical market-specific internals that outperforms the "one size fits all" engines by a factor of 50 or so. Vertica is an example of this claim in the data warehouse market. It achieves blindingly fast warehouse performance by: