I've had 60 watt CFL bulbs in lamps for years but just yesterday put a 100 watt one next to a regular 75 watt one in 2 hanging fixtures in my kitchen. The 75 watt regular looks a lot brighter than the 100 watt (and yes I waited). I was never really convinced about the 60 watt ones either; they all seemed lower light. I see that the box for the 100 watt says '1600 lumens, almost the 1650 lumens of a 100 watt regular bulb' so 50 off 1650 wouldn't explain it. I just wonder if anyone else feels the same way, since I suppose it's all been measured officially, and it must be my subjective view. Not a big deal I know.

I searched Qs and found a good answer:
However, most times the incorrect "color" lamp is chosen. This is a bit complicated to explain, I will do my best:

I find that the color temperature of a CFL chosen is often incorrect when replacing an incandescent lamp, which is 2700 Deg Kelvin, (AKA 27K). Most times people are not familiar with CT ratings, and buy any CFL. I see that most stores offer 41K or at best 35 K. Look for a CFL rated 27K to imitate a incandescent lamp.

Even a CFL lamp rated 27 K will not imitate a incandescent lamp exactly with the same color rendering, difficult to create a fluorescent lamp with the same color characteristics. What would imitate a incandescent lamp would need to be a CFL at 27 K with a Color Rendering Index of 1. This does not exist, most have a CRI of 82. Need to look for a CFL lamp with the highest CRI rating possible.

Learn About Light: Color Rendering: GE Commercial Lighting Products

The best I could find is the following link, click on Interactive Color Booth, a separate window will pop up, and you can chose different lamp sources and compare the color of any two:

Learn About Light: Selecting the Best Color Lamp: GE Commercial Lighting Products

If a 41K lamp, even if the proper wattage or light output is similar to the incandescent lamp is chosen, a 41K lamp with the will make an area seem dark, due to color temperature and CRI.

I hope I made some sense explaining this, and how important it is to use a warm color CFL with a high CRI rating when using in place if incandescent lamps. I use them thruout my home, and in many commercial applications where color and CRI is very important, and the results are fanastic. No one can tell there are no incandescent lamps.