Civ 5 is an entertaining game and has the basic foundations of an amazing game after a few more patches and an expansion or two. Civ IV was the same way when it came out. You really CAN NOT compare Civ 5 on release to Civ IV in its current form. Civ IV has been worked on for years longer than Civ 5, has had two major expansions which GREATLY improved gameplay, and has had millions of hours of play testing with TONS of feedback from players. If you want to keep playing Civ IV because its a more polished and more enjoyable game, thats fine, but lets not pretend that Civ IV was ANYTHING like it currently is when it first released, and I think we can expect Civ V to undergo a similar process and eventually become superior to Civ IV in just about every way.
That said, I have also stopped playing Civ V for the time being (though I spent a good number of hours on it already). Too little variability in the game play, too many basic features missing (who the hell thought it was okay to release this game without the ability to tell automated workers to leave existing improvements alone?), and the AI needs a lot of work still. This patch is a huge step in the right direction, and I'll probably fire the game up again in the next couple days to see how all the changes affect the overall gameplay.