First off I'm a Toyota fan so i'll add that disclaimer right now.
Anyways I really think Lexus offers the best value for the money.
Firstly, most Lexuses are independent platforms, not gussied up Toyotas. Lexus ES350 and the LX share platforms with Toyota Landcruisers and Camrys but otherwise, they're all independent cars that aim for the euro brands and usually do very well.
Acura on the other hand is basically a nicer Accord or Euro Accord or what have you and the same with Infiniti. Lots of platform sharing. Also, much more use of FWD in Acura and Infiniti which is not exactly what Luxury vehicles are perceived to be. In essesce, you can get most of what the Acura TL is in a Honda Accord V6 manual. You can get most of the MDX and RDX in the respective Pilot and CRV, you can get most of the G35 in a 350z and Fx in a Murano and QX in a Armada. The only big changes in Acura are engines and Infiniti is, well a nicer interir and maybe a engine. Of course there are exceptions like the RL and M but that's it. With Lexus, if you want a IS, SC, LS, GS or RX, theres no Toyota replacement.
Also if you look at Lexus, you get the most reliability for the money while also getting specialized production lines for the custom platform models. For example, on the Lexus LS460, 460L and 600h, the cars are produced at the factory with that statistically produces the cars with the least problems per 100 vehicles. The factory guys hand buff the steering wheel 3 times and during off days, have specialized training tasks like differentiating nail polish containers to train their eye for subtle color differences and closing their eyes to guess exactly how many nuts and bolts are in their hand without looking.
It's attention to detail like that which is found in very few cars besides say, AMG, M// Division, Porsche, the Phaeton, Maybach, Ferrari and etc(aka, the Who's who of luxury models) After all, "The devil's in the details" and when you look at a lot of BMW's with the huge panel gaps and then look at an ordinary Camry(I have a 2002) in which you cant even slip a piece of paper in between the bumper and fender, you start to wonder...