... BUT, it's not that hard to master. W/O making any assumptions, here are my thoughts:
Did you use the same paint? (It's a formality - I had to ask.) Did you prime/seal all the walls you're looking at BEFORE you painted? And not just 1 vs. the other? Did you use the right 'nap' on the roller? (Depending on the texture, there are different naps.) Did you stir the paint well? Is the lighting (natural or otherwise), creating an 'illusion'?
Now, for home painting, here are some useful tips:
Read the instructions on the can BEFORE you leave the paint store. This way, if you have any ?'s, you're there to ask. Always stir the paint well before you pour it. As you transition from one can to another, 'mix' the little amount of paint from Can A with some of the 'newer' paint in Can B. This way, your paints will 'blend' in case there's a slight difference of color between 2 identical cans of paint. If you're gonna try to strrrrreatch a can of paint, plan on a 2nd top coat. It's not worth trying to do this. My retailer (with whom I have no affiliation), will take back any unopened cans. Over-lap your work. Allow ample time to dry. Clean your 'tools' well, and when the roller gets 'clogged' with solids, spend $2.00 and buy a new one. And be sure the roller is dry before you use it. (A hair dryer will speed things up if you're in a jam.) Last but not least, buy your paint from a reputable Paint Retailer (found in the Yellow Pages under Paint - Retail.) You won't find much support on this Forum/BBS for the paint that's sold in the Big Box stores like Home Depot, Lowes, etc., etc.. It's worth the extra $$$ for a better paint. (My personal favorite is Finnaren and Haley. I just bought $106 worth of paint and primer/sealer from them on Monday morning!)
Most homeowners should be able to get buy with these tips. If you have more info or need more guidance, post up. My best to ya and hope this helps.