So we looked into this back in 2008 or so, when my wife invested in some fancy kitchen knives (expensive but well worth it). One source we trust immensely for everything about cooking is America's Test Kitchen, which is a show on PBS. If you don't know about them, they investigate old/classic recipes and come up with new recipes by scientifically varying ingredient amounts, cooking times, etc, to figure out the best way to cook stuff. It's pretty fascinating and their recipes are always a home run for us.
They have a segment reviewing kitchen tools and equipment, and it's very helpful. They are good at weeding out the gimmicks, and the junk, and the overpriced tools. When it came to sharpening knives, they ended up recommending a very simple knife sharpener you can find in a hardware store:
AccuSharp 1 Knife Sharpener - - Amazon.com
We've had one of those for 9 years and it continues to do an awesome job. I think it was $7 when I bought it at the hardware store years ago. We also have a truing bar, which is used to straighten the blade edge periodically between sharpening.
My dad is a traditionalist and likes using a whetstone, but I showed him the sharpener and even he was surprised. It got the knives noticeably sharper than he could. It gets them razor sharp, so be extra careful (although dull kitchen knives are more dangerous than sharp ones from what I have heard).