If we base it purely on how often we see problems in a forum (considering how long I've been in this forum), LCD is the least reliable, LCOS in the middle, and DLP is the most reliable.
Newer color wheels really do not break that often, I've been in most every thread in these forums for years, I see hundreds of times more LCD dust blob or panel degradation issues than I see color wheel problems. A lot of the posts I see on color wheel issues are related to much older projectors often purchased in the used market, many of them I see are on Optomas or very old Mits (almost never on a New Mits).
For instance, in the Benq w6000, Mits hc4000, and Mits hc3800 threads, I have seen but only a handful total color wheel problems in 4 years. We know these projectors have been big sellers, with thousands of users. Definitely a few more color wheel issues in the Benq thread than the Mits (which is almost unheard of), but neither one have enough to be alarming.
In the Panny 4000 and Epson 8700ub threads, I have seen hundreds of reports of dust blobs and other issues. I can confidently say that DLP is more reliable than LCD on average.
For sure on some of the older model DLP's, color wheels were the achilles heel, it just isn't that way anymore (it can still happen, but it's much rarer).