The 2009-10 season is in the books, but the summer break gives us a chance to offer up critiques on various programs. TV Fanatic will grade and review as many as we can.

Most recently, we took on shows ranging from The Good Wife to Gossip Girl and 90210. Today, we're on to Grey's Anatomy, a series we're finding uniquely difficult to assess.

The show is, to a point, a victim of its own success, and the standards it set over its first few years. Our B- grade seems low, since there is still so much we love about Grey's.

We just believe the show can be that much better.

What did we think of the sixth season of the ABC medical drama? Who was its best character? Did it meet expectations? Where are we headed next? Read on and comment.

Best character: We've always loved Meredith, Derek, Cristina and Bailey so much, let's focus on two that really developed this season - Alex and Mark. Both had some terrific story arcs that showed new facets of their personalities, which proved more complex than you might have originally thought. Most, if not all of the characters shined at times, but these two stood out.

Season Six brought out a different side of Mark Sloan.

Worst character: Izzie. Truthfully, this is more a critique of the actress who played her and how the situation was handled, which was somewhat out of the writers' hands. Izzie recovered, only to be fired, come back and leave again for good? As viewers, we felt as jerked around as Alex. To a lesser degree, we could've done without some of the Mercy West crew.

Best use of guest stars: Jason George beats out some worthy competition for this one. He was awesome, and easy on the eyes, as Ben, Bailey's anesthesiologist love.

Best episode: "Give Peace a Chance." The season finale was great and there were many strong weeks, but we absolutely loved this Derek-centric episode from early in the season. It was one of Patrick Dempsey's best performances and a moving story to boot.

Best storyline: The maturation of Meredith and the evolution of married life with Derek is a joy to watch. While we wouldn't call Cristina and Owen's struggles a joy, Sandra Oh and Kevin McKidd are so terrific that they're no less compelling. All things Calzona. The introduction of Sloan Jr., the more we got to know her and how she affected him. The mesmerizing finale.

Worst storyline: While no single story line bothered us or made our eyes roll, there was a bit too much experimenting at times: A swarm of Mercy West doctors all at once, flashbacks, crossovers, episodes told from 12 perspectives, characters starring one week and barely seen the next. If the show lacked one thing for parts of what was overall a fine season, it was consistency.

At its best when: The core characters we love blend humor with emotion as they grapple with real-life professional and relationship situations we can relate to.

At its worst when: There's too much going on, or the action feels forced by "game-changing" events (sometimes necessary, but can become overkill as well).

Hopes for 2010-11: Grey's Anatomy is still a great show, and one we loyally watch for characters, the writing, the medical and personal story lines - all of it.

However ...

Despite our appreciation for all the serious, dramatic, funny and romantic action the show brings, there has been a shift in its direction, which to a point is inevitable.

As years pass, new characters are introduced that viewers don't take kindly to, since they've become attached to the original characters and are resistant to change.

Also, some of the episodes start to feel a bit repetitive, whether they're relationship-driven or over-the-top sweeps-week extravaganzas like shootings or disasters.

Teddy and Jackson: Subtraction by addition?

The writers can return Grey's to its past glory by remembering what made it successful, focusing on the core cast and keeping some people and plots more peripheral.

Teddy's past with Owen, Mark's daughter, April's obsession with Derek and other stories were all fine on their own merit, but detract from what the show does best.

The cast has just gotten so big that there is no room for all the characters at times, and some of these sudden declarations seem to absolutely come out of nowhere.

Kim Raver and Jesse Williams are great, but the writers need to decide where the show is going and what their priorities are to keep things more focused next year.

Otherwise, history is destined to repeat itself, and we'll have another season lacking in continuity and feeling scattered, with occasional huge accidents to spice it up.

Enjoyable? Certainly. But it could be better.

Overall grade: B-.

What were your impressions of the season - and what would you like to see in Season Seven? What characters and episodes worked best in your view? Discuss below!

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.