This is a cheesesteak town, as we all know. And the city will always have that steak as its signature griddle move, its crossover dribble, its split-fingered strikeout pitch. But if you take a closer look at what menus are really pushing in town, from the high-end bistros down to the newest chains, you'll find more kitchen energy is devoted to reinventing the cheeseburger than anything else.

As I tasted more and more evidence of this phenomenon, I knew I could no longer avoid the project I had put off for more than a decade: The Great Burger Quest.

Part of me feared the Quest because I had an inkling where it might lead. But really, I had no idea it would go this far.

When you love a food as much as I love burgers - and I covet cheeseburgers, in particular - undertaking a mission like this is to flirt with a dangerous, lipid-laced obsession.

It is one thing to simply seek out the best burger in the land, objectively nibbling my way through a few dozen would-be contenders. But what actually happened during the six months of steady research, as I devoured more than 50 burgers across the region, surprised even me:

I began dreaming of the ideal patty when I slept at night, constantly mulling the perfect combination for every sandwich. I composed burger poetry, and, then, one night, I unexpectedly awoke humming a cheeseburger tune.

This little burger roundup - or shall I say "ground-up" - literally acquired its own soundtrack (with a music video! Check it out online at http://go.philly.com/cheeseburger).

It also reconnected me to the roots of my own eating passions, and it revealed some telling truths about the state of food in Philadelphia, and America at large.

Of course, I also savored my share of memorable burgers along the way - both spectacular and atrocious.

The Quest took me from the grease-shined griddles of classic luncheonettes to the white linen of some of the city's most luxurious tables, as well as every gastro-pub, funky diner, and new-school burger chain in between.

It was a challenging regimen to maintain. But by the end, I found myself still singing.

I'm not the only one obsessed with a great burger, it turns out. It's a national phenomenon, according to the North American Meat Processors Association, which this month declared "high-end burgers the hottest trend in food service." Burger boutiques are all the rage in Manhattan. And in Vegas you can spend $5,000 for a truffle-spiked foie gras-Kobe beef double at Fleur de Lys at Mandalay Bay.

If you want proof of its pull on Philadelphia, too, just go to Rittenhouse Square. Long the epicenter of our city's fine-dining ambitions, Rittenhouse also turns out to be ground-round zero of our Hamburg Renaissance, with stellar examples at every level of culinary ambition.

As you might expect, the Square sports luxury burgers galore, from the rarefied Kobe patties at Barclay Prime and Lacroix at the Rittenhouse, to the gargantuan and juicy show-offs at Rouge, to the exquisitely crafted house-ground burger on house-baked brioche at Matyson. There are innovative gastro-bar burgers, like the blue cheese-stuffed wonder at the Good Dog, which was the inspiration for my song, "Cheeseburger, I Hold." And there are also veteran luncheonette chefs, like Vincent McKnight at Snow White, who still knows how to make a classic, pretense-free patty for less than $5. So tasty, I had to order another.

Not far from Rittenhouse Square is also Center City's first branch of Five Guys, which is rapidly becoming the local leader of a national trend to upgrade the fast-food-chain burger. Five Guys aspires to something along the lines of California's legendary In-N-Out, but it's a far cry from the quality of that amazing West Coast institution.

The local franchise of the Virginia-based Five Guys chain has plans to open 50 locally, and the Chestnut Street location sizzles up fresh, never-frozen burgers that are an obvious cut above McDonald's. The fries are among the best in town.

But this harried Five Guys also exemplifies so many of the pitfalls of careless burger cookery. The patty-smashing grill chefs lean on those burgers with all their might, wringing them of juice like a dry sponge. Then the assembly line stacks so many clunky toppings on with a final, bun-crushing squish that the sandwich falls to bits when you open the wrapping. Stay simple at Five Guys - one patty and one topping only (like jalapeños). Ask the bun crusher to back off, and you'll be happy.

Fresh, never-frozen meat is a bottom-line criterion for burger greatness - because the ice crystals leach juices from the meat and compromise its texture, according to William Henning, professor emeritus of meat science at Penn State. But all that fresh-meat goodness can be wasted with one big spatula smack.