Their naming scheme is okay for what it is. Comparing CPUs from different segments makes little sense anyhow. While there could be more of a differentiator between 2c4t parts and everything above, it really isn't an issue.
For mobile: celeron->pentium->i3->i5->i7. All 2 cores, last three 4 threads. Last two with Turbo Boost. i7 has larger caches, some extra features.
Mobile >28W: Only i5 and i7 matter. i5 is 4c4t, i7 is 4c8t. Done.
Desktop: Celeron + pentium = useless low-end sh*t. i3: 2c4t. i5: 4c4t. i7: 4c8t.
HEDT: All i7, all the way. They're all high-end anyway.
Will a 45W i5 kick the a** of a 15W i7? Of course it will. But you won't find a 15W i7 in anything claiming truly high performance. And anyone thinking an i7 ultrabook is comparable to a desktop i7 or even a high-performance laptop i7 deserves what they get. Keeping the same nomenclature across series makes sense in terms of branding, keeping things consistent. Making people understand that different types of PC have different base capabilities isn't really Intel's responsibility.