That you were at the elite 4. Which gives me a standing point against which I can judge the levels of your pokemon.
You werent specific about which game. I assumed you meant my most recent game, which was platinum.
First of all, 60-70 is really high. I mean, the champion doesn't even have pokemon past level 66. You are supposed be ~10 levels lower than the champion. That is what makes it a tactical challenge rather than a simple brute force battle of stats. Usually, my pokemon are level 45-55. These levels are easily reachable just going through the normal passages, fighting the trainers, and doing any sidequests. It sounds like you are just bad at the battling, and have to put in some extra grind to compensate.
I'm well aware of that, and yes at those levels the champion wasnt hard. This was in fact not the team I beat the elite 4 with the first time - I cant remember what that consisted of, I think it had 3 starter pokemon from the various games. Not a 2nd gen one though. Probably Blastoise, Sceptile, Infernape and 3 others. Not sure. I think I was 50-60 (in platinum) when I beat the elite 4. I got to 60-70 after raising the second team in the hopes of doing that mountain quest, whatever it is, end goal was to eventually do the gym leader rematches. As far as I remember, those were pretty high.
No I'm not bad at battling, and thanks for jumping to conclusions when you in fact know absolutely nothing. I tend to play on the cautious side of things in Pokemon, so I make heavy use of STAB and type advantages, generally going for one hit KOs if at all possible. However, while thats true, just to get to a high enough level to even beat the last gym leader or elite 4 required me to do a lot of grinding in diamond. First tried (in diamond, NOT PLATINUM) when my lowest level poke was probably 46, highest probably 55. Remember, elite 4 in diamond are at a higher level in diamond than platinum, by 5 levels. Was eventually beaten by Cynthia after scraping through Lucian.
Platinum didnt require any grind, because as I said by that time I had my second DS and Diamond, so I could breed in Diamond and trade them over to Platinum. And I had a number of lucky eggs due to farming at this point (and getting the lucky eggs in itself was a lot of grind, to minimize later grind).
Secondly, I was talking about Emerald, since that is the one you didn't finish. If you are past all the gyms, you should be able to get Rayquaza, which, at level 70, can wipe the floor of all the elite 4.
I dont think my highest level pokemon in emerald was above level 40. 42 maybe. I had beaten all of the gym leaders, as I said. Team consisted of vileplume, Swampert, Heracross, Manectric, Swellow and someone else, might have been a dark pokemon (not mightyena though).
It would have taken me a lot of grind to get them to a high enough level to beat the elite 4. As a rule, I dont use legendaries in battle.