Having just wrapped up a MASSIVE redesign of this very portfolio, it stands that now is the perfect time to put down some thoughts about what a creative portfolio website is, is not, can be, and definitely should not be. This last rebuild started as a ground-up project, went through about three major revisions, and finally... helped me settle on a color scheme. I then scrapped everything else and rebuilt it around all the little details I liked from it's previous incarnations, as well as some industry window-shopping and advice from fellow designer / developers.
What should a good portfolio be?
A portfolio's purpose is to show two things: who you are, and what you can do. Especially in the web design and development world, this means there's a lot at stake in which foot you're putting forward. Whereas a video game designer, for example, certainly needs a good looking site, it's ultimately a showcase for his or her work in another medium. A quality theme or quirkily creative concept will do wonders, as long as it accents that main goal. As a web developer, however, your showcase should be your showcase, as well as one of your finest pieces. Now we're getting meta folks: showcase your showcase by building a good showcase.
High stakes doesn't mean everything has to necessarily be any one 'thing' though. If minimalism is your hallmark, go for it. It's certainly a favorite of mine. If you prefer complexity, skeuomorphism, whatever floats your little digital boat, do it the best you can. Here's the caveat though: make it stand out from the work you are putting into the portfolio. Even if you're into a very niche field, and want to keep all your work in the same vein, your portfolio is a chance to show potential clients what you CAN do, even outside your normal work. It doesn't have to be as stark as day and night, but it shouldn't be so similar as to say that you're obviously a one-trick-pony.
Make It Yours
Whatever your stylistic course of action, do everything you can to make it yours. If you favor back end development over front end design, put in as many (sensible) bells and whistles you can that show you know how to make da Vinci look like an amateur. I'm a fan of putting in at least one thing (front or back) that impresses non-savvy users and potential clients, as well as at least one more complex and subtle, to act as a hidden hand shake of quality for other insiders of your industry. Make it an innovative trick in the responsive design flow. Build a PHP function or Javascript bit that blows your mind if you don't see it coming. Take something you've got a knack for, and polish more than ever before.
Finally, get some input. This can be the trickiest stage of the process, and it is very different for every person. Some folks should get input while they're still sitting at the drawing board stages to help focus their ideas. Others should knock out some well fleshed-out demos or even partial sites (I'm in this camp 99% of the time) and then sit back and contemplate what they've made. If you've got good, professional contacts you trust, ask them for their opinions. Go to communities like LinkedIn groups or the /r/web_design and /r/design_critiques boards on Reddit. Also make a point of talking to a few folks outside the industry as 'normal users' to temper the opinions of everyone else who lives and breathes this stuff every day. Perspective can be a wonderful thing.
Once you've got it all together, put it in a list. Go down the list and see what really merits listening to. If you know one adviser is a notable print-designer who has included in-depth thoughts on your typography, feel free to put more weight there than in a fellow back end web developer with little comparable typographic experience. Don't let this advice overwhelm and completely alter your project. If, however, so much of the advice seems sound enough that it leaves very little of your project standing, perhaps it's time to go back to the drawing board. No shame there. Keep what you liked of the old site (colors, logos, whatever), and build from there with the old advice in mind.
You're on your way, just keep pushing. Don't give up, and only second guess yourself so many times. Caution is good, but a perpetually under-construction site impresses nobody.