What is the best class for pve.

Basically I'm a veteran player over 6 years but when i started playing I was a kid and I realy don't know what class to make a new character with. I only play pve I don't pvp or wvw. I just prefer to do raids and currently main a thief but wondered if there was a better class.

Debating whether one profession is better than another is like trying to compare druid to power dragonhunter. Every single profession has their own role in PvE, some are better at power damage, some are better at condition damage and others are healers/boon appliers. If you prefer reading benchmarks, then SnowCrows has them for you and you can make your choice over which profession seems better than thief in terms of damage.

Personally, benchmarks don't really matter to me. I don't like the idea of choosing a profession based on benchmarks or using benchmarks as a decisive factor for choosing professions in end game content. Every profession has a role in raids and yes, that also includes necromancer. Don't limit yourself to playing just one profession, it gets stale playing the same profession over a long period of time. What I would recommend for you is to try out the professions you're interested in, see if you enjoy playing them or watch videos showing how people play with raid builds. As the old saying goes, "Variety is the spice of life".