In terms of the sheer power of the base damage of their attacks, I guess they are. But there are other factors that come into play when determining how strong a card is or isn't. One of those factors is energy efficiency for how much damage you do as well as what types of effects the attack has. Both Lugia ex and Rayquaza C Lv. X (yes, that's the card's full name - it's not just Rayquaza Lv. X) require 3 different types of energy to use those attacks, and getting all 3 of those into play can be hard. They also don't have a lot of HP, especially by today's card standards, so they can be pretty easily knocked out for prizes, and HP is another factor in how strong a card is. An example of a card that has solid HP and can attack very efficiently for very little energy is Gyarados from Stormfront. It can do up to 90 damage for no energy, provided you have 3 Magikarp in your discard pile, and it has 130 HP itself, which is not bad for a Stage 1 Pokemon by any means.
Personally, I'd argue that this Gyarados can be just as strong, if not stronger, than those other two cards, seeing as it can easily have Lugia ex and Rayquaza C Lv. X knocked out before either of those two cards have their attacks powered up, and the fact that it has more HP than either. There are many cards that can beat the setup speed and energy efficiency of Gyarados, though, because Gyarados needs some trainers to be able to setup so much damage so quickly.