Playing C Ionian, then D Dorian, E Phyrgian, etc. is pointless, I agree. The point of modes is that each mode has it's own sound. Try playing C Lydian, then C Ionian, C Mixolydian, C Dorian, C Aeolian, C Phyrgian, and finally C Locrian (I put them in this order, because that's the order from "brightest" to "darkest" in sound). Now, if you're soloing over something in C Major, C - Am - F - G, for example, try using one of the above C modes. It's not about using relative modes, but rather paralell modes. Don't use C Ionian then A Aeolian, F Lydian, and G Mixolydian, that would be just giving one set of notes 7 names. Try C Lydian followed by C Ionian, C Mixolydian, then C Lydian again...
Oh, also, to the best of my knowledge, modes evolved on the organ centuries ago. Modes are just as useful on the piano as they are on the guitar, however.
"You must stab him in the heart with the Bone Saber of Zumacalis... well, you could stab him in the head or the lungs, too... and the saber, it probably doesn't have to be bone, just anything sharp lying around the house... you could poke him with a pillow and kill him."
- Aqua Teen Hunger Force, The Universal Re-Monster
