So much fail by OP in this thread...
1) Most played != Most powerful. Most played = Most popular. Which DGs are actually strong and weak is entirely and only dependent on how they are played at high levels of competition. The most played stat is completely corrupted by the results of average/noob games.
1A) In fact, this fact has come up before in a previous thread. Why do Forces of Light always lose Pantheon? Because too many players pick Reg, and then get horribly slaughtered by UB/LE from Forces of Darkness.
2) Any DG can take down a tower if you ignore him for long enough. But no DG can take down a tower if theres a DG defending it, unless hes been fed all game or something. Considering that most towers are in the creep paths, where you should always have people anyways (to gain experience, gold, hold flags, etc) its not especially difficult to prevent your towers from getting raped.
3) Regulus has some decent abilities, but as others have said, hes below average compared to the rest of the cast. Sedna, UB, Oak, and LE are generally better.